test: timer: fix warning under clang

Clang raises the following warning:

../test/timer.cpp:26:56: error: field 'events' is uninitialized when used here [-Werror,-Wuninitialized]
    TimerTest() : rc(sd_event_default(&events)), timer(events)

Initialize 'events' to resolve.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Ia637709bf578e38211eeb2bbc56bb592b99004a6
diff --git a/test/timer.cpp b/test/timer.cpp
index 8621967..48152b0 100644
--- a/test/timer.cpp
+++ b/test/timer.cpp
@@ -11,7 +11,7 @@
 {
   public:
     // systemd event handler
-    sd_event* events;
+    sd_event* events = nullptr;
 
     // Need this so that events can be initialized.
     int rc;