Disable ztest deadman timer

The ztest deadman timer has been causing false positives in the
testing VMs.  To make it easier to spot possible regressions
I'm disabling this timer.  The buildbot test infrastructure
will still mark ztest instances which take to long to complete
as failures.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #1018

cmd/ztest/ztest.c

@@ -5289,11 +5289,13 @@ ztest_resume_thread(void *arg)
 
 #define GRACE	300
 
+#if 0
 static void
 ztest_deadman_alarm(int sig)
 {
 	fatal(0, "failed to complete within %d seconds of deadline", GRACE);
 }
+#endif
 
 static void
 ztest_execute(int test, ztest_info_t *zi, uint64_t id)
@@ -5550,11 +5552,13 @@ ztest_run(ztest_shared_t *zs)
 	    (thread_func_t)ztest_resume_thread, spa, TS_RUN, NULL, 0, 0,
 	    PTHREAD_CREATE_JOINABLE)), !=, NULL);
 
+#if 0
 	/*
 	 * Set a deadman alarm to abort() if we hang.
 	 */
 	signal(SIGALRM, ztest_deadman_alarm);
 	alarm((zs->zs_thread_stop - zs->zs_thread_start) / NANOSEC + GRACE);
+#endif
 
 	/*
 	 * Verify that we can safely inquire about about any object,