sanity check memcached availability before running tests against it

Change-Id: I40fff70cbf395e7fe42530155074f75dd116034c
Closes-Bug: 1296794
Improve language in update_password() validation error

Change-Id: I728af11c6d652c2937e6da80b96a5c3f337bae76
Related-Bug: 1239757
Merge "sanity check memcached availability before running tests against it"
Merge "Improve language in update_password() validation error"