BluetoothAudioHAL: Avoid deadlock for get Providers Factory 2.1

Single instance of mutex is used for getting all Providers Factories.
Calling GetProvidersFactory 2.0 but having 2.1 instance can cause dead
lock scenario.

Bug: 173538746
Tag: #feature
Test: start Bluetooth with set vinf ProvidersFactory set to 2.1
Sponsor: jpawlowski@
Change-Id: I642adb779391196296dfe8db2a352ebdcf711070