roomservice: handle devices with underscores

This change correctly handles devices with underscores in their
name even if there is a device with the same name after the last
underscore (spyder, umts_spyder) by not allowing any underscores
in the manufacturers name.

Without this change, spyder gets resolved to:
device/motorola_umts/spyder
device/motorola/spyder

Only the last one is valid.

With this change, both spyder and umts_spyder get resolved correctly.

Change-Id: I0c95ff126d827a2d6b58875dfcb9327e999f4913