Bug#19535 mysql-test-run cannot handle crashing test cases

- Make mysql-test-run.pl restart a crashed/stopped process if it was expected it should crash.
 - Added testcase for "crash_commit_before", which tests behaviour when server crashes just before commit.
  * The testcase first write a small var/tmp/master0.expect file indicating expected crash
  * Then sets "DEBUG" variable to for example "d,crash_commit_before" and then executes a commit.
  * The server will crash and be brought back up by mysql-test-run.pl
  * Test case will then wait for the process to come back online before continuing.

mysql-test/t/crash_commit_before.test

@@ -0,0 +1,22 @@
+--source include/have_debug.inc
+
+CREATE TABLE t1(a int) engine=innodb;
+START TRANSACTION;
+insert into t1 values(9);
+
+# Setup the mysqld to crash at certain point
+SET SESSION debug="d,crash_commit_before";
+
+# Write file to make mysql-test-run.pl expect crash and restart
+--exec echo "restart" > $MYSQLTEST_VARDIR/tmp/master0.expect
+
+# Run the crashing query
+--error 2013
+COMMIT;
+
+# Call script that will poll the server waiting for it to be back online again
+--source include/wait_until_connected_again.inc
+
+SHOW CREATE TABLE t1;
+
+SELECT * FROM t1;