Fixes #5375

Fixes #5764

* fixed a bug in which failures from a with_* loop were not being
  caught correctly, leading to tasks continuing when they should stop
* when ignore_errors is enabled, the failure will no longer count
  towards the number of failed tasks

Merge pull request #11301 from msabramo/include_inventory_file_in_unable_to_find_inventory_file_error_msg

Add inventory file to "Unable to find" error msg

E.g.:

    $ ansible gabriel -m ping -i ssh_config.py
    ERROR! Unable to find an inventory file (ssh_config.py), specify one with -i ?

add simple prefix filtering to vmware inventory

Significantly speeds up inventory collection on systems with many
excluded machines.

support instances with no public ip

Avoids a race condition where previously the registered variable message
was being sent after the 'host_task_ok' message, meaning the next task
may be started before the var is registered, leading to an undefined
variable error

default to private ip if the instance doesn't have a public ip assigned. (causes list index out of range error otherwise)

Simplify serf inventory plugin

fixes 11296 where the groups does not have all the groups

using newly added `EnvironmentConfig` class in `serfclient`.

See https://github.com/KushalP/serfclient-py/pull/17

for tags with empty value, do not append separator

plugins/inventory/serf.py: Use SERF_RPC_* env vars

This makes the Serf inventory plugin use the `SERF_RPC_ADDR` and
`SERF_RPC_AUTH` environment variables that the `serf` command-line tool
already uses.

These can be used to get Serf data from a remote node instead of
requiring the ansible control host to be running a serf agent and to be
a member of the serf cluster.

Bugfix: win_checksum

Don't panic if AIX's uname doesn't support -W

The current code expects "uname -W" on AIX to always succeed. The AIX 5
instance I have doesn't support the -W flag and facts gathering always
crashes on it.

This skips some WPAR handling code if "uname -W" doesn't work.

Fixes for FreeBSD get_memory_facts

- swapinfo on FreeBSD 6 (maybe 7 too?) doesn't support the "-m" flag for
  fetching amounts in megabytes. This patch fetches amounts in kilobytes
  and divides by 1024 (and also returns the result as an int instead of
  a string).

- When no swap is configured, swapinfo prints a header line and nothing
  else:

    $ swapinfo
    Device         1K-blocks     Used    Avail Capacity

  The old version unexpectedly parsed that header line and emitted
  nonsense values like:

    "ansible_swapfree_mb": "Avail"
    "ansible_swaptotal_mb": "1K-blocks"

  This version emits those items altogether.

fixed become password handling

Fixes #11132

Add serf inventory plugin

Add inventory plugin for [Serf](https://serfdom.io/).
Requires [`serfclient` Python module](https://pypi.python.org/pypi/serfclient).