Modify method to get MQDescriptor for unsynchronized FMQ.

The modified method adds a new parameter specifying
if a new unsynchronized FMQ needs to be set up by the server
or if it is to return an MQDescriptor to
an unsynchronized FMQ that has already been configured
by the server(if one exists)

Bug: 35319190
Test: FMQ unit tests
Change-Id: I64a5b356a2761faaeeea6fdd2c3a7da9b60f0016