Check connection status when returning in NimBLEClient::Connect.

There is a chance to become disconnected before returning from the onConnect callback so the connection
status should be checked when returning from client connect.

src/NimBLEClient.cpp

@@ -284,7 +284,8 @@ bool NimBLEClient::connect(const NimBLEAddress &address, bool deleteAttibutes) {
     m_pClientCallbacks->onConnect(this);
 
     NIMBLE_LOGD(LOG_TAG, "<< connect()");
-    return true;
+    // Check if still connected before returning
+    return isConnected();
 } // connect