Always use 'bluetooth' for checking loggability

The liblog library implements caching to save the value
of the most recently used log tag and save on calls to
read system properties.

However the bluetooth native code is using too many different
log tags and this cache is constantly being evicted. This change
ensures that the cache has longer lifetime.

Test: m com.android.btservices
Test: Manual, check perfetto traces
Bug: 346429202
Flag: EXEMPT, log change
Change-Id: I1514547d001695f15d80cfefc9a16f2a06e583b7