Bug 1095480 - enable mochitests for linux64 mulet

Test task:
http://docs.taskcluster.net/tools/task-inspector/#BUiInBaMTsai5SLu1sxPzg/0

11:56:29     INFO -  2499 INFO Passed:  110565
11:56:29  WARNING -  2500 INFO Failed:  36
Hrm is this now part of mozharness?