tests/regressions: Allow regression test for bug 914931 to be skipped.
daemon: If /proc/modules doesn't exist, linuxmodules optgroup is disabled.

It likely means the kernel was compiled without modules support.
daemon: md: Whitespace fixes.
daemon: list-md-devices: Check if a /dev/md<X> device is valid before returning it.

For reasons not fully understood, if md is linked into the kernel (and
not a module), a /dev/md0 device node is created.  However this is not
a real RAID device.  For example running mdadm --detail /dev/md0 will
fail on it.

Check the /dev/md<X> devices are real RAID devices before returning
them from the list-md-devices API.
virt-list-filesystems: Fix to use $g->canonical_device_name instead of homebrew function.

The homebrew function didn't recognize /dev/ubd* device names, and in
any case using the API function is shorter and clearer.
uml: Fix guestfs_canonical_device_name API to understand /dev/ubd* paths.
uml: Fix maximum number of disks.
uml: Fix race when multiple handles are used in parallel.

See comment for explanation.
uml: tests: Skip some tests which cannot work with the UML backend.
uml: tests/disks: Fix test so it can cope with /dev/ubd* device names.
uml: tests/mountable: Skip tests that need qcow2.
uml: tests/lvm: Fix assumption that broke /dev/ubd* device names.
uml: tests/luks: Fix assumption that broke /dev/ubd* device names.
uml: tests/md: Fix test to cope with /dev/ubd* device names.
uml: tests/md: Skip test-inspect-fstab.sh since it needs qcow2.
uml: tests/qemu: Fix tests so they work without support for qcow2.
uml: tests: edit: Skip test since it needs qcow2.
uml: fuse: Skip test since it needs qcow2.
uml: resize: Skip test since it needs qcow2.
uml: sparsify: Skip test since it needs qcow2.