OSXBTCentralManager - fix details discovery (iOS/OS X)

-serviceForUUID: fails to find included service and returns a nil
for a valid service previously discovered.

Task-number: QTBUG-52324
Change-Id: I9f4f8b1f3d3a78879344ace0170e23c03921d648
Reviewed-by: Alex Blasche <alexander.blasche@theqtcompany.com>