remove-cache-tier action failing @mitaka

Trusty-Mitaka cache tier amulet tests are failing @master/next charms.

01:48:35.614 2016-04-15 15:34:06,746 test_403_cache_tier_actions DEBUG: Testing cache tiering
01:48:35.614 2016-04-15 15:34:10,194 run_action INFO: Running command: juju action do --format=json ceph-mon/0 create-cache-tier cache-mode=writeback cache-pool=hot backer-pool=cold
01:48:35.614
01:48:35.614 2016-04-15 15:34:20,880 run_action INFO: Running command: juju action do --format=json ceph-mon/0 remove-cache-tier cache-pool=hot backer-pool=cold
01:48:35.614
01:48:35.614
01:48:35.614 juju-test.conductor.019-basic-trusty-mitaka DEBUG : Got exit code: 1
01:48:35.614 juju-test.conductor.019-basic-trusty-mitaka RESULT : FAIL
01:48:35.614 juju-test.conductor INFO : Breaking here as requested by --set-e
01:48:35.614 juju-test INFO : Results: 4 passed, 1 failed, 0 errored
01:48:35.627 make: *** [functional_test] Error 1
01:48:35.627 ERROR:root:Make target returned non-zero.
01:48:35.652 Returned: 1
01:48:35.652 ! Amulet test failed.

...

2016-04-15 15:33:47 INFO remove-cache-tier 2016-04-15 15:33:47.729794 7efc13979700 -1 Errors while parsing config file!
2016-04-15 15:33:47 INFO remove-cache-tier 2016-04-15 15:33:47.729797 7efc13979700 -1 read_conf: ignoring line 30 because it doesn't end with a newline! Please end the config file with a newline.
2016-04-15 15:33:47 INFO remove-cache-tier Error EPERM: 'forward' is not a well-supported cache mode and may corrupt your data. pass --yes-i-really-mean-it to force.
2016-04-15 15:33:47 INFO worker.uniter.jujuc server.go:172 running hook tool "juju-log" ["Removing the cache tier failed with message: "]
2016-04-15 15:33:47 DEBUG worker.uniter.jujuc server.go:173 hook context id "ceph-mon/0-remove-cache-tier-3990087660024766415"; dir "/var/lib/juju/agents/unit-ceph-mon-0/charm"
2016-04-15 15:33:47 INFO juju-log Removing the cache tier failed with message:
2016-04-15 15:33:47 INFO worker.uniter.jujuc server.go:172 running hook tool "action-fail" ["remove-cache-tier failed. Removing the cache tier failed with message: "]