HAMMER VFS - Minor bug (caught by assertion panic)
* A snapshot can sometimes contain visible inodes whos nlinks count is 0,
essentially the snapshot 'catches' the file in the middle of being deleted.
* HAMMER was attempting to truncate the data for such inodes if the file
were opened and then closed, and failed to check whether the inode was a
snapshot or a current inode. This flowed through until it hit an assertion
designed to detect precisely that case.
* Fixed by adding a check to determine if the inode is a snapshot and/or
the filesystem is mounted read-only.
Repored-by: Max <herrgard@gmail.com>