self.dev.fsamroy/.osamroy on the scan server is a generic bec_lib
Positioner proxy rebuilt from serialized device info, not the real
ophyd instance. tolerance was only a plain __init__ attribute, so it
was dropped during serialization and flomni_rotation()/rotation()
crashed with AttributeError: 'Positioner' object has no attribute
'tolerance'. Register tolerance in USER_ACCESS so it serializes and
is reachable via RPC like controller already is.