Pause the req before checking access

/to @bajtos @ritch 
/cc @bnoordhuis 

The PR fixes the issue reported by: https://github.com/strongloop/loopback-storage-service/issues/7

With the fix, the test case https://gist.github.com/bajtos/9388676 is passing.

@bajtos, do you want to add the test into loopback-storage-service?