afs: Use common cleanup code for lockctl EINVAL

afs: Use common cleanup code for lockctl EINVAL

afs_lockctl has common cleanup code in the 'done' label. Use it here,
instead of trying to duplicate it.

Currently this code path appears to not be dropping the discon lock,
which this rectifies.

Change-Id: I136a78bc3235454db7e3d69bb79b0061cfcab265
Reviewed-on: http://gerrit.openafs.org/8196
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>