Please describe the problem:
The webdav tries to calculate the mount_prefix, by traversing up the directory it is asked to mount, until it encounters an error.
It fails to remove a trailing slash from the final path, resulting in extra mounts happening.

Steps to reproduce:
1. Go to dav://webserver/dav/docs in nautilus. A mount is now created, with mount_prefix=="/dav/" (verify with gvfs-info dav://webserver/dav/docs)
2. Use the up-arrow to go one directory up
3. An extra mount is created, with mount_prefix=="/dav"


Actual results:
An extra mount is created, meaning that two mounts now exist for the same location.

Expected results:
No extra mount created.

Does this happen every time?
Yes

Other information: