votequorum: Don't update expected_votes display if value is too high

If expected_votes was set via the library but the calculation
decides it's too high, then an error is correctly returned but
the value is still set in the nodes' expected_votes field and
turns up in the corosync-quorumtool display.

This patch separates out the quorum calculation from the updating
of expected_votes per node to prevent this from happening.

Signed-off-by: Christine Caulfield <ccaulfie@redhat.com>
Reviewed-by: Jan Friesse <jfriesse@redhat.com>