MB-32650: Change collections feature code from 0x9 to 0x12
MB-32650: Change collections feature code from 0x9 to 0x12

As per protocol changes, switch to feature 0x12 so cbworkloadgen
continues to work.

Change-Id: Ia45a0dd0672208cc1914eb5afefda93e12d90424
Reviewed-on: http://review.couchbase.org/103630
Tested-by: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Patrick Varley <cbb7353e6d953ef360baf960c122346276c6e320@couchbase.com>

couchbase/couchbase-cli,couchbase/couchbase-cli