gvfs should ignore snap package mounts

[Oliver Grawert]

when removing a snap package gvfs shows a device in the unity panel for a split second while the squashfs is unmounted during package removal.

ideally gvfs should ignore all snap package operations since the package mounts should never be used directly by users.

running in one terminal:
sudo snap remove <snapname>

while in another terminal gvfs-mount --monitor is running i get the following output:

ogra@styx:~$ gvfs-mount --monitor
Monitoring events. Press Ctrl+C to quit.

Volume added: 'Datenträger 66 MB'
Volume changed: 'Datenträger'
Volume removed: 'Datenträger'

this only happens on snap removal, not when installing a snap (nothing is printed in the --monitor terminal during install)

[Oliver Grawert (ogra)]

not sure if the fix for this needs to be in gvfs or in snapd, so i added a snapd bugtask as well.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.