MB-10496: Add jemalloc as a cbdeps dependancy for Ubuntu

Adds jemalloc cbdeps for Ubuntu 12.04 & 14.04.

Change-Id: I89c65b418c6f71baf56d8cf7fd6b5098df649090
Reviewed-on: http://review.couchbase.org/43079
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>