Add Priority and Issue sections for memcached relocation fix

Change-Id: Ia79f6232316c4bc19d2c5e5a9a05e86c6048bfaa
Reviewed-on: http://review.couchbase.org/42612
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Brett Lawson <brett19@gmail.com>