add isSuccessful method to McuMgrResponse

mcumgr-android-lib/src/main/java/io/runtime/mcumgr/response/McuMgrResponse.java

@@ -109,6 +109,15 @@ public McuMgrErrorCode getRc() {
         return mRc;
     }
 
+    /**
+     * Returns true if the response payload contains a return code of 0 or no return code. In other
+     * words, return true if the command was a success, false otherwise.
+     * @return return true if the command was a success, false otherwise
+     */
+    public boolean isSuccess() {
+        return rc == McuMgrErrorCode.OK.value();
+    }
+
     /**
      * Get the response bytes.
      * <p>
@@ -122,10 +131,7 @@ public byte[] getBytes() {
     }
 
     /**
-     * Get the response payload in bytes.
-     * <p>
-     * If using a CoAP scheme this method and {@link McuMgrResponse#getPayload()} will return the
-     * same value.
+     * Get the response payload bytes.
      *
      * @return the payload bytes
      */