PCBC-562: Allow to disable caching connections
PCBC-562: Allow to disable caching connections

When couchbase.pool.max_idle_time_sec is zero, all cached connections
will be released in the end of request

Change-Id: Idb442aa37573bf6ef61096a98f90b2b85b3083f2
Reviewed-on: http://review.couchbase.org/99561
Tested-by: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Sergey Avseyev <87f6d5e4fd3644c3c20800cde7fd3ad1569370b3@gmail.com>

couchbase/php-couchbase,couchbaselabs/php-couchbase,couchbaselabs/php-couchbase,couchbase/php-couchbase,couchbaselabs/php-couchbase,couchbaselabs/php-couchbase,couchbase/php-couchbase,couchbase/php-couchbase