prov/psm: fix the return code of fi_cq_read for error completions

When an error entry is created from PSM status, the function returned 1
incorrectly. The correct way is to continue to the CQ dequeue step, where
the error entry will be discovered and the proper value will be returned.

Signed-off-by: Jianxin Xiong <jianxin.xiong@intel.com>
Merge pull request #411 from j-xiong/master

prov/psm: fix the return code of fi_cq_read for error completions