Fix Coverity CID 174746: Control flow issues (DEADCODE).

Testing if curl_handle != NULL or rc != SLURM_SUCCESS was already done
in the right above if/else statements, jumping to the consequent goto
cleanup label if needed. Thus the removed test was never going to be
evaluated to true, and Coverity properly warned about this.

Regression introduced in commit 5f5e6472 (code cleanup).