test: timer: Initialise all variables

The ManagedTimer does not initialise the integer 'interval_' variable.

This is set before used, and should not break - but for completeness
(and to cover static analysers) initialise the variable in the
initialiser list.

Fixes: 034ea86802 ("test: Add timer test")

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

test/timer.cpp

@@ -19,7 +19,8 @@ using namespace libcamera;
 class ManagedTimer : public Timer
 {
 public:
-	ManagedTimer() : Timer()
+	ManagedTimer()
+		: Timer(), interval_(0)
 	{
 		timeout.connect(this, &ManagedTimer::timeoutHandler);
 	}