Prevent invoking callbacks from `synchronized` block.

The callback implementations might call InfoMediaManager getter calls
resulting in a deadlock.

Test: atest InfoMediaManagerTest, on a device.
Flag: com.android.media.flags.enable_suggested_device_api
Fix: 422720290
Change-Id: Ie41df25780f17bc0b8acd2a4e32be94c3bd08573