ceph: add checking of wait_for_completion_killable() return value
The Coverity Scan service has detected the calling of
wait_for_completion_killable() without checking the return
value in ceph_lock_wait_for_completion() [1]. The CID
1636232
defect contains explanation: "If the function returns an error
value, the error value may be mistaken for a normal value.
In ceph_lock_wait_for_completion(): Value returned from
a function is not checked for errors before being used. (CWE-252)".
The patch adds the checking of wait_for_completion_killable()
return value and return the error code from
ceph_lock_wait_for_completion().
[1] https://scan5.scan.coverity.com/#/project-view/64304/10063?selectedIssue=
1636232
Signed-off-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>