Fix isUsbMassStorageConnected() will always return true
Fix isUsbMassStorageConnected() will always return true

After UMS mounted, isUsbMassStorageConnected() will always return true even if USB is disconnected.
It's because mUmsEnabling will always be ture.

Change-Id: Ib24b2359ea2684eb0a9faeb880f383e87630e6e1

xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base