[Coverity CID :187318] Error handling issues in /tests/posix/pthread_key/src/pthread_key.c

[mandarcthorat1]

Static code scan issues seen in File: /tests/posix/pthread_key/src/pthread_key.c
Category: Error handling issues
Function: test_pthread_key
Component: Tests
CID: 187318
Please fix or provide comments to square it off in coverity in the link: https://scan9.coverity.com/reports.htm#v32951/p12996

[nniranjhana]

#9085 which fixes this issue has been merged, hence closing this issue.