files: Amend overlayfs unit descriptions with path information

files: Amend overlayfs unit descriptions with path information

Having something like

Starting Overlayfs directories setup /home...
Starting Overlayfs directories setup /root...
Finished Overlayfs directories setup /home.
Finished Overlayfs directories setup /root.
Mounting Overlayfs mount unit /home...
Mounting Overlayfs mount unit /root...
Mounted Overlayfs mount unit /root.
Mounted Overlayfs mount unit /home.

is much more informative than

Starting Overlayfs directories setup...
Starting Overlayfs directories setup...
Finished Overlayfs directories setup.
Finished Overlayfs directories setup.
Mounting Overlayfs mount unit...
Mounting Overlayfs mount unit...
Mounted Overlayfs mount unit.
Mounted Overlayfs mount unit.

Especially as the number of overlayfs mount units increase.

Signed-off-by: Esben Haabendal <esben@geanix.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>