[Libguestfs] Remaining btrfs patches

[Matthew Booth]

[PATCH 1/7] mount: Add mount_vfs_nochroot

This is significantly reworked from before. umount is gone as
discussed, and variable motion is minimised.

[PATCH 2/7] btrfs: Update btrfs_subvolume_list to take

Already provisionally ACKed. Previous comment was that cleanup could
be tidier. I looked into creating a new cleanup function for fs_buf,
but it isn't possible (or simple, anyway) in this case for 2 reasons:

1. You'd need 2 arguments passed to the cleanup function, not one.
Without fs->type you don't know whether fs_buf has been mounted or
not.

2. You can't catch and report an error.

[PATCH 3/7] mountable: Make list-filesystems return btrfsvols

Already provisionally ACKed.

[PATCH 4/7] New internal API: internal_parse_mountable
[PATCH 5/7] inspect: Update inspect_os to use mountables
[PATCH 6/7] btrfs: Make a stub Fedora btrfs guest for inspection
[PATCH 7/7] mountable: Test inspection of fedora image

Not previously reviewed.