This is used for the new calls back from the data provider.

This is needed in order to assure the memcache is properly and promptly
cleaned up if a user memberships change on login.

The list of the current groups for the user is sourced before it is
updated and sent to the NSS provider to verify if it has changed after
the update call has been made.

This set of functions enumerate the user's groups and invalidate them all
if the list does not matches what we get from the caller.

This set of functions enumerate each user/group from all domains
and invalidate any mmap cache record that matches.

These functions can be called from the nss responder to invalidate
records that have ceased to exist or that need to be refreshed the
first time an application needs them.

There used to be an overlinked dependency that's gone now, so
to fix a build error add CLIENT_LIBS to sss_ssh_knownhostsproxy_LDFLAGS.

v2:
Fix sss_ssh_authorizedkeys linking as well.