init: add log w/ service PID

We could combine this with the existing log, but I
wouldn't want to make that appear later.

Ironically, adding this log to try to reduce logs.

Bug: 36785118
Test: :) adb logcat -d | grep "started service" | wc -l
131

Change-Id: I38f4e9740871aa256eef0c62e897038eb46871a5
diff --git a/init/service.cpp b/init/service.cpp
index 87d9c3a..cce24c3 100644
--- a/init/service.cpp
+++ b/init/service.cpp
@@ -755,6 +755,9 @@
 
     NotifyStateChange("running");
     reboot_on_failure.Disable();
+
+    LOG(INFO) << "... started service '" << name_ << "' has pid " << pid_;
+
     return {};
 }