Key-Manager module integration.

Key-Manager module integration.

Key-Manager provides secure storage for user keys, certificates and other, private data.
Key-Manager database is encrypted using user password.
Key-Manager module must know the user login, logout and password change events.
This change integrates the Key-Manager with PAM - Key-Manager listens to session events to lock/unlock
the database and password interface to know the user password change - and to re-encrypt the database
key using new password.
pam_key_manager_plugin.so is marked as optional in system-auth config.

Change-Id: Ifd1158f8b82fa28f8ae9442b42c2f2e7723068c7