Permit 0 length writes.

Change-Id: I087d0074c8d9e13ce814187475966da94f693fc0
diff --git a/libsysutils/src/SocketClient.cpp b/libsysutils/src/SocketClient.cpp
index ff2315b..c9c7417 100644
--- a/libsysutils/src/SocketClient.cpp
+++ b/libsysutils/src/SocketClient.cpp
@@ -62,6 +62,10 @@
     const char *p = (const char*) data;
     int brtw = len;
 
+    if (len == 0) {
+        return 0;
+    }
+
     pthread_mutex_lock(&mWriteMutex);
     while (brtw > 0) {
         if ((rc = write(mSocket, p, brtw)) < 0) {