CameraService: Check Thread::run for failed threads.

While a thread failing to launch is somewhat catastrophic, checking the
result and printing the error / returning early is good practice.

Test: Ran CameraThreadSafetyTest.
Change-Id: I8c1d3fe197ef8af631960dd286096287de9a280e
diff --git a/services/camera/libcameraservice/device3/Camera3Device.cpp b/services/camera/libcameraservice/device3/Camera3Device.cpp
index 0845a64..acee2ab 100644
--- a/services/camera/libcameraservice/device3/Camera3Device.cpp
+++ b/services/camera/libcameraservice/device3/Camera3Device.cpp
@@ -229,7 +229,12 @@
 
     /** Start watchdog thread */
     mCameraServiceWatchdog = new CameraServiceWatchdog();
-    mCameraServiceWatchdog->run("CameraServiceWatchdog");
+    res = mCameraServiceWatchdog->run("CameraServiceWatchdog");
+    if (res != OK) {
+        SET_ERR_L("Unable to start camera service watchdog thread: %s (%d)",
+                strerror(-res), res);
+        return res;
+    }
 
     return OK;
 }