In daemon mode, arv-mount should set up the fuse connection before
forking to the background, so that any failures to set up are reported
to the user.
CollectionReader can throw exceptions (for example, when passing an
argument that is not a manifest or collection UUID). Trap those and
print an error message, instead blowing up the fuse driver.
Merge branch '0000-arv-mount-bugfixes'

This closes #2831