locking: Clarify message for removed locks
locking: Clarify message for removed locks

Just being told that a lock doesn't exist can be confusing. One case
were this happens is when a job (e.g. instance modify) waits for a job
removing the instance (e.g. export with remove).

Signed-off-by: Michael Hanselmann <68b67885ff74281219b4a4be33cc20fd45078d7c@google.com>
Reviewed-by: Iustin Pop <acf83a5274f31a43af6b914614365999469c1a31@google.com>

andir/ganeti,mbakke/ganeti,ganeti/ganeti,ganeti/ganeti,bitemyapp/ganeti,apyrgio/ganeti,apyrgio/snf-ganeti,ganeti-github-testing/ganeti-test-1,mbakke/ganeti,apyrgio/ganeti,leshchevds/ganeti,dimara/ganeti,yiannist/ganeti,apyrgio/snf-ganeti,leshchevds/ganeti,yiannist/ganeti,yiannist/ganeti,grnet/snf-ganeti,grnet/snf-ganeti,ganeti/ganeti,andir/ganeti,ganeti-github-testing/ganeti-test-1,bitemyapp/ganeti,onponomarev/ganeti,dimara/ganeti,onponomarev/ganeti,mbakke/ganeti,andir/ganeti,leshchevds/ganeti