Fix problem where mysql-test-run.pl fails to start up the mysqld after a failed test. Shows up on win hosts where one failed test case make subsequent ones fails with error "Could not open connection 'default': 2003 Can't connect to MySQL server on 'localhost'" 
Fix problem where mysql-test-run.pl fails to start up the mysqld after a failed test. Shows up on win hosts where one failed test case make subsequent ones fails with error "Could not open connection 'default': 2003 Can't connect to MySQL server on 'localhost'" 


mysql-test/lib/mtr_process.pl:
  Reset the associated "pid" of masters and slave when building the list of processes to shutdown.

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