Make sure mCurrentUsbFunctionsRequested flag be updated currectly

There is a situation that getCurrentUsbFunctions callback function will
be invoked before mCurrentUsbFunctionsRequested flag updated, thus, gadget
will be reset during boot completed. Make sure mCurrentUsbFunctionsRequested
flag be updated before getCurrentUsbFunctions callback function invoked.

Bug: 121448199
Test: Verified that gadget reset does not happen
Change-Id: Id8b58d9ccd3f62c976d1292575a06554bef622a4
Merged-In: Id8b58d9ccd3f62c976d1292575a06554bef622a4
Signed-off-by: Howard Yen <howardyen@google.com>
(cherry picked from commit 3b747d31)