vsh: Don't put VSH_OT_ALIAS onto list of completions

vsh: Don't put VSH_OT_ALIAS onto list of completions

We've invented VSH_OT_ALIAS type for --option so that we can
rewrite some --options (e.g. fix spelling). For instance
blkdeviotune command uses this feature heavily:
--options-with-dash are preferred over old
--options_with_underscore. Both versions are supported but only
the new ones (not aliased) are documented and reported in --help.

Except for options completer, which happily put also aliased
versions in front of user's eyes.

Note, there is a second (gross) way we use aliases: to rewrite
options from --oldoption to --newoption=value (for instance
--shareable option of attach-disk is an alias of
--mode=shareable). And just like with the previous group - don't
generate them into the list of possible options.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Jonathon Jongsma <jjongsma@redhat.com>