fixes CC-12: return error instead of panic when listing invalid template...

... id

DEMO:
```
# plu@plu-9: serviced template list
TEMPLATEID				NAME		DESCRIPTION
0b05fed05123a6167d3858e9f58d8a5e	Zenoss.core	

# plu@plu-9: serviced template list doesnotexist
unable to find template by id: doesnotexist
```