define ceph::key.

Provides keyring management.

Handles cephkeys (cephx), creating keyring files, injecting keys into
the keyring via ceph and ceph-autotool tools. Includes support for
multiple keys in the same keyring file (as this is supported by the
ceph-authtool tool).

Includes rspec system puppet for validation.

Change-Id: Ib3c4832ffcff61ab42ae221cdd5a5bfb76ee36c5
Implements: blueprint puppet-ceph#key
Merge "define ceph::key."