Bug#21188  	mysqlimport returns random exit code  - Only handle return codes from 'pclose' greater than zero as errors.  - It appears pclose can return -1 with errno set to ECHILD although the executin process completed successfully. 
Bug#21188  	mysqlimport returns random exit code
 - Only handle return codes from 'pclose' greater than zero as errors.
 - It appears pclose can return -1 with errno set to ECHILD although the executin
process completed successfully. 


client/mysqltest.c:
  Only handle return codes from 'pclose' greater than zero as errors.

natsys/mariadb_10.2,natsys/mariadb_10.2,ollie314/server,flynn1973/mariadb-aix,flynn1973/mariadb-aix,davidl-zend/zenddbi,flynn1973/mariadb-aix,natsys/mariadb_10.2,davidl-zend/zenddbi,davidl-zend/zenddbi,davidl-zend/zenddbi,ollie314/server,davidl-zend/zenddbi,ollie314/server,ollie314/server,flynn1973/mariadb-aix,davidl-zend/zenddbi,davidl-zend/zenddbi,davidl-zend/zenddbi,ollie314/server,ollie314/server,flynn1973/mariadb-aix,flynn1973/mariadb-aix,ollie314/server,natsys/mariadb_10.2,natsys/mariadb_10.2,flynn1973/mariadb-aix,flynn1973/mariadb-aix,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,ollie314/server,davidl-zend/zenddbi,davidl-zend/zenddbi,flynn1973/mariadb-aix,flynn1973/mariadb-aix,davidl-zend/zenddbi,ollie314/server,natsys/mariadb_10.2,flynn1973/mariadb-aix,ollie314/server,slanterns/server,ollie314/server,natsys/mariadb_10.2