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).

Update syslog_json.py

localhost is better than locahost ;)

added vaultfile class for action and lookup plugin usage

should fix #11275

Allow AdHocCLI to be more flexible for overriding

aslo added comment clarifying why we do this

- moved check prompt/password functions to connection, make more senes there
- TODO: consider moving make_become to connection from connection_info
- removed executable param that was never overriden outside of connection info

fixed mixup with remote password vs become_password