snap info reports incorrect service status

[Roger Peppe]

I ran `snap info /var/lib/snapd/cache/$snaphash` and it prints information that its service is disabled and inactive, which is misleading, because the actual service was enabled and active.

Perhaps `snap info` should not try to print the service status when run on a file

Example output:

 # snap info /var/lib/snapd/cache/51856ffe6b04e621f84236289f54f696be65f57626375a295e576cba0f18a73fa35d39611a22bb0dc6dfd38393bb6e9a
 path: "/var/lib/snapd/cache/51856ffe6b04e621f84236289f54f696be65f57626375a295e576cba0f18a73fa35d39611a22bb0dc6dfd38393bb6e9a"
 name: hydroctl
 summary: Hydro power control system
 version: 15 -
 build-date: 31 days ago, at 15:38 UTC
 license: unset
 description: |
   Experimental power control system
 services:
   hydroctl.hydroserver: simple, disabled, inactive