Fix help text being incorrect with multiple args

E.g. "docker foobar run" would have printed "Command not found:
foobar" and printed the help text for "run". It should instead
print the root help message for docker.

Signed-off-by: Ben Firshman <ben@firshman.co.uk>
Update "official repos" doc to mention 100 char short desc limit

The Hub no longer accepts short descriptions over 100 characters.

Signed-off-by: Andrew Page <admwiggin@gmail.com>
Merge pull request #8928 from tianon/not-200-chars-anymore

Update "official repos" doc to mention 100 char short desc limit
Fix deadlock in ps exited filter

Fixes #8909

Signed-off-by: Alexandr Morozov <lk4d4@docker.com>
Merge pull request #8929 from LK4D4/fix_filter_hang

Fix deadlock in ps exited filter
Merge pull request #8927 from bfirsh/dont-pass-args-to-help-when-command-doesnt-exist

Fix help text being incorrect with multiple args