Users can change their current context by executing airshipctl config
set-context [NAME]. The use-context subcommand was recently introduced
to replace this behavior. This change removes the original behavior.
Closes #56
Change-Id: Ib962d1d69a198c897aff18759fef869ee04d1beb
Signed-off-by: Drew Walters <andrew.walters@att.com>