Convert tags parameter from list to dict in launch_ec2.

1.9 requires that you import * from ansible.module_utils.basic
and to_native doesn't exist in 1.9, however this works fine for
our uses on 16.04.

https://github.com/ansible/ansible-modules-core/blob/stable-2.2/system/systemd.py

It supports assumed roles (using AWS STS).
1.9.3 only supports standard credentials.

As a site operator,
I want to tag AWS resources,
so that I can more easily query/filter my VPCs.

Nothing ground-breaking here, but I did have a use-case for it.

This will connect to a cluster, find the hidden secondaries and upgrade
them to the current version specified in the mongo_3_0 play.

This required the creation of a new library module since our two current
ones return rs.status and call replSetReconfig, but neither return
rs.config, and rs.config is what tells you if a host is hidden and the
priority, which are needed for this.

We were implicitly relying on mongo to return the list of members in
their _id order, which is absurd and I have no idea how we didn't catch
it previously.

We could do a little list comprehension to pull out the member with the
same _id,  but it seemed easier to just sort both lists and retain the
original intent.

If a git version is specified as a branch, and the commit referred to is
already on the local working tree, but the branch is not, then the
checkout will fail.

This is because the Ansible 1.9.3 module would check to see if the
commit was already present, and if so, did not fetch. This meant the
branch wasn't defined in the local working tree.

This can happen if you make a branch but there aren't any changes on the
branch.

I believe the loops will be easier to debug in the long run.
Essentially, we have a shallow compare loop in check_config_subset
and then a deep compare loop in is_member_subset.

Both functions allow extra information in the config that comes back
from Mongo, since Mongo tracks things like votes: slaveDelay: etc that
may not be reflected in the configuration you pass in.

Do a bit more error checking before asking for the replica set.

The new mongo play wants to be able to run this against an unconfigured
Mongo to find out "Do you even have a replica set?" which this can now
answer (the try/except portion).

In the case where mongo was started without a replSet configured (or
running getCmdLineOpts fails for an OperationFailure reason), we
return a dictionary where status is not included to allow tasks to
detect the failure.  Unfortunately, Ansible doesn't provide an easy way
to log back why you didn't get a replica set doc.

Documentation improvements for this module

Discusses the return values and some examples of checking them.

Simplify get_replset

If the find_one for a replset fails, just return None.
We don't need to worry about getting back a dictionary which contains a
'config' key (presumably this is from an earlier iteration of the code
which called getReplSetStatus which does act like that).

Rather than raising the exception, use the friendly error here.

I assume the raise/module.fail_json double header was leftover cruft
from earlier development.

Make the module work without rs being configured

Initially, this module always tried to find and connect to a primary,
however, during replica set initialization, there is no primary so we
need to fall back to just connecting to the machine specified.

This is detected by catching the replSetGetStatus failure and falling
back to the bare get_client method which refactors the connection.

Now you can provide a (slightly simpler) cluster config and it'll
idempotently make it so.

Later, zip_to_dict calls ast.literal_eval which requires this be a
string.  We can remove this *and* the literal_eval call, however that
would require testing all the places we call these util functions.

Delete when PR merges: <https://github.com/ansible/ansible-modules-core/pull/2542>
Fixes issue reported in <https://github.com/ansible/ansible-modules-core/issues/2150>