libsysutils: const correctness fixes + remove some debugging

Signed-off-by: San Mehat <san@google.com>
diff --git a/include/sysutils/SocketListener.h b/include/sysutils/SocketListener.h
index 30d050d..68dcb8f 100644
--- a/include/sysutils/SocketListener.h
+++ b/include/sysutils/SocketListener.h
@@ -37,8 +37,8 @@
     int startListener();
     int stopListener();
 
-    void sendBroadcast(int code, char *msg, bool addErrno);
-    void sendBroadcast(char *msg);
+    void sendBroadcast(int code, const char *msg, bool addErrno);
+    void sendBroadcast(const char *msg);
 
 protected:
     virtual bool onDataAvailable(SocketClient *c) = 0;