Remove the isBound() check for HotwordDetectionService.

There will be a race condition (Ex:Create AlwaysOnHotwordDetector
twice quickly) where it will miss unbinding HotwordDetectionService
and clearing HotwordDetectionServiceProvider when using the
isBound() check for HotwordDetectionService.

Because we use "ServiceConnector.Impl" to create the connection,
it is unnecessary to use isBound() function to check if the
HotwordDetectionService should be unbound.

Bug: 195457729
Test: atest CtsVoiceInteractionTestCases
Test: atest CtsVoiceInteractionTestCases --instant
Test: manual - DSP and non-DSP
Change-Id: Ib74e0dc9364af3713007b115f7d170bf6e833810