Fix setServerParams to not always set snapshot pending

Only updates should set snapshot pending. Setting the server params for
the first time should not set snapshot pending. If it did, then just
initializing the recovery agent would cause a snapshot to be made, even
if it contained no keys. Also, setting the snapshot to the same value as
it was previously should not set snapshot pending, for the exact same
reason. If the server params were to change, however, for some reason,
then a new snapshot must be made, so that it can be synced to the correct
vault.

Bug: 74949975
Test: runtest frameworks-services -p \
      com.android.server.locksettings.recoverablekeystore

Change-Id: Ie09284553f922de869be7bcd577d0f0eb9d0bbd3