This way it is possible to specify the UUID of the LUKS device instead
of the libguestfs device name to decrypt a device during the inspection.
Make the usage of the new luks_uuid API conditional, so other projects
using the common submodule do not require a libguestfs version bump.
(cherry picked from commit bb4a2dc17a78b53437896d4215ae82df8e11b788
in libguestfs-common)
PT: the documentation was amended manually.