test-throttle: Fix uninitialized use of burst_length

ThrottleState::cfg of the static variable 'ts' is reassigned with the
local one in the do_test_accounting() and then is passed to the
throttle_account() with uninitialized member LeakyBucket::burst_length.

Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Message-Id: <1564502498-805893-2-git-send-email-andrey.shinkevich@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tests/test-throttle.c

@@ -558,6 +558,8 @@ static bool do_test_accounting(bool is_ops, /* are we testing bps or ops */
     BucketType index;
     int i;
 
+    throttle_config_init(&cfg);
+
     for (i = 0; i < 3; i++) {
         BucketType index = to_test[is_ops][i];
         cfg.buckets[index].avg = avg;