[build] rename the macro OPENTHREAD_ENABLE_ANDROID_PROPERTY (#1061)
[build] rename the macro OPENTHREAD_ENABLE_ANDROID_PROPERTY (#1061)

This commit renames the macro name OPENTHREAD_ENABLE_ANDROID_PROPERTY
to OTBR_CONFIG_ANDROID_PROPERTY_ENABLE and declares the variabe
`aInstance` as a unused variable to avoid compile error.
openthread/ot-br-posix,openthread/borderrouter,openthread/borderrouter,openthread/ot-br-posix,openthread/ot-br-posix,openthread/ot-br-posix,openthread/ot-br-posix,openthread/borderrouter,openthread/borderrouter,openthread/borderrouter,openthread/ot-br-posix,openthread/borderrouter