glocalfile: Handle smb2 filesystem type

`G_FILE_ATTRIBUTE_FILESYSTEM_TYPE` is not set for CIFS mounts with
`vers=2.0` option, or newer. Add `smb2` to the list of known filesystems.
It is also reported by `stat -f`:
https://github.com/coreutils/coreutils/blob/master/src/stat.c
10 jobs for wip/oholy/cifs-splice in 42 minutes and 2 seconds (queued for 4 seconds)
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