adbd: add a log message on start.

Make it easier to identify adbd's PIDs for coverage purposes by adding
an explicit log message to grep for.

Test: manual
Change-Id: I47e13417c0d9adb7d427414fd70c218f988909f5
diff --git a/daemon/main.cpp b/daemon/main.cpp
index 9e02e89..55b7783 100644
--- a/daemon/main.cpp
+++ b/daemon/main.cpp
@@ -301,6 +301,8 @@
         setup_adb(addrs);
     }
 
+    LOG(INFO) << "adbd started";
+
     D("adbd_main(): pre init_jdwp()");
     init_jdwp();
     D("adbd_main(): post init_jdwp()");