Increase deadlock_timeout some more in the deadlock-hard isolation test.

The previous value of 5s is inadequate for the buildfarm's
CLOBBER_CACHE_ALWAYS animals: they take long enough to do the is-it-waiting
queries that the timeout expires, allowing the database state to change,
before isolationtester is done looking.  Perhaps 10s will be enough.
(If it isn't, I'm inclined to reduce the number of sessions involved.)

src/test/isolation/specs/deadlock-hard.spec

@@ -63,7 +63,7 @@ step "s7a8"	{ LOCK TABLE a8; }
 step "s7c"	{ COMMIT; }
 
 session "s8"
-setup		{ BEGIN; SET deadlock_timeout = '5s'; }
+setup		{ BEGIN; SET deadlock_timeout = '10s'; }
 step "s8a8"	{ LOCK TABLE a8; }
 step "s8a1"	{ LOCK TABLE a1; }
 step "s8c"	{ COMMIT; }