mapclient: use symbolic constant for downloading attachments am: c8dd0795

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Bluetooth/+/3114303



Change-Id: Ic3390d9546a1b5e634ee89486f7fb4490a7c865e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>