Avoid unnecessary quorum checks when quorum is not enabeld on a node

Currently decisions_view() calls _decisions_meets_quorum() which calls _decisions_count_voters "SELECT COUNT(DISTINCT CONCAT(uid,vote_source)) AS voters FROM {votingapi_vote} WHERE content_id=%d". This query was taking ~2 minutes to run in an environment with ~7 million rows in the votingapi_vote table.

The attached patch changes the code flow so that if both the quorum # of voters required and percentage are 0, further queries related to quorum are not performed when viewing the node.