CID 1522781: Argument cannot be negative

[maskit]

Looks like the last fix made new ones.

ssl_session_reuse/src/config.cc

CID 1522782: Argument cannot be negative (NEGATIVE_RETURNS) [[select issue](https://scan6.scan.coverity.com/defectInstanceId=34843144&fileInstanceId=166426161&mergedDefectId=1522782)]
   	
CID 1522781 (#1 of 1): Argument cannot be negative (NEGATIVE_RETURNS)
4. negative_returns: fd is passed to a parameter that cannot be negative.
 89  close(fd);