Leverage the new cliff command class attribute (_description)
to get the help of a command, this allows us to mark strings
for translation. We could not do this before since the help
was grabbed from the docstring.
This also depends on a new release of cliff and a bump to the
minimum level in osc's requirements.
Closes-Bug: 1636209
Depends-On: Id915f6aa7d95a0ff3dc6e2ceaac5decb3f3bf0da
Change-Id: I8673080bb5625e8e3c499feaefd42dfc7121e96f
0ef8535036