fix for Bug#18848  "SIGHUP crashes the server" (v2)
fix for Bug#18848  "SIGHUP crashes the server" (v2)


sql/log.cc:
  check whether log tables were initialized, before trying to
  flush them during sighup processing. Then use logger THD
  for flush.

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