Added OS_ prefix so tests wait for these threads

* This would create a deadlock on the main thread in the past, Roboelectric 4.0 may have fixed this.

Author: jkasten2

OneSignalSDK/onesignal/src/main/java/com/onesignal/OneSignalRestClient.java

@@ -66,23 +66,23 @@ public static void put(final String url, final JSONObject jsonBody, final Respon
          public void run() {
             makeRequest(url, "PUT", jsonBody, responseHandler, TIMEOUT, null);
          }
-      }).start();
+      }, "OS_REST_ASYNC_PUT").start();
    }
 
    public static void post(final String url, final JSONObject jsonBody, final ResponseHandler responseHandler) {
       new Thread(new Runnable() {
          public void run() {
             makeRequest(url, "POST", jsonBody, responseHandler, TIMEOUT, null);
          }
-      }).start();
+      }, "OS_REST_ASYNC_POST").start();
    }
 
    public static void get(final String url, final ResponseHandler responseHandler, @NonNull final String cacheKey) {
       new Thread(new Runnable() {
          public void run() {
             makeRequest(url, null, null, responseHandler, GET_TIMEOUT, cacheKey);
          }
-      }).start();
+      }, "OS_REST_ASYNC_GET").start();
    }
 
    public static void getSync(final String url, final ResponseHandler responseHandler, @NonNull String cacheKey) {