xstat: Add the residency RPC to the list of fs ops

Include the ResidencyRpc in the list of fs operation numbers that
can be display by xstat_cm_test.

Caught by coverity (#989029)

Change-Id: Ib8059fe53e5254d212722db59c05a0f0822883e2
Reviewed-on: http://gerrit.openafs.org/9320
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>