KVM: x86: fix uninitialized variable use on KVM_REQ_TRIPLE_FAULT

If a triple fault was fixed by kvm_x86_ops.nested_ops->triple_fault (by
turning it into a vmexit), there is no need to leave vcpu_enter_guest().
Any vcpu->requests will be caught later before the actual vmentry,
and in fact vcpu_enter_guest() was not initializing the "r" variable.
Depending on the compiler's whims, this could cause the
x86_64/triple_fault_event_test test to fail.

Cc: Maxim Levitsky <mlevitsk@redhat.com>
Fixes: 92e7d5c8 ("KVM: x86: allow L1 to not intercept triple fault")
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/x86.c

@@ -10280,8 +10280,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 				vcpu->run->exit_reason = KVM_EXIT_SHUTDOWN;
 				vcpu->mmio_needed = 0;
 				r = 0;
+				goto out;
 			}
-			goto out;
 		}
 		if (kvm_check_request(KVM_REQ_APF_HALT, vcpu)) {
 			/* Page is swapped out. Do synthetic halt */