be more user friendly when I mess up commands
be more user friendly when I mess up commands

In particular:

* If I run lxc without args, print a list of the available commands instead of
  saying "give me a subcommand".
* If I give an invalid command name, give the list of commands available.

Signed-off-by: Tycho Andersen <10c18fcb898ee6b17d6575d444b125d10b3f4d6a@canonical.com>

jsavikko/lxd,stgraber/lxd,lxc/lxd,hallyn/lxd,erikmack/lxd,jsavikko/lxd,beni55/lxd,mikemccracken/lxd,jumpstarter-io/lxd,georghopp/lxd,rcj4747/lxd,benaryorg/lxd,Malizor/lxd,pcdummy/lxd,chrisglass/lxd,lxc/lxd,chrisglass/lxd,erikmack/lxd,mikemccracken/lxd,techtonik/lxd,smoser/lxd,mikemccracken/lxd,rrva/lxd,pcdummy/lxd,rrva/lxd,dustinkirkland/lxd,rcj4747/lxd,mjeanson/lxd,pcdummy/lxd,mjeanson/lxd,atxwebs/lxd,erikmack/lxd,yura-pakhuchiy/lxd,sl1pm4t/lxd,stgraber/lxd,atxwebs/lxd,stgraber/lxd,stgraber/lxd,hallyn/lxd,achanda/lxd,yura-pakhuchiy/lxd,lxc/lxd,jensg-st/lxd,lxc/lxd,beni55/lxd,stgraber/lxd,benaryorg/lxd,beni55/lxd,techtonik/lxd,ericsnowcurrently/lxd,smoser/lxd,ericsnowcurrently/lxd,Malizor/lxd,jumpstarter-io/lxd,benaryorg/lxd,sl1pm4t/lxd,chrisglass/lxd,Skarlso/lxd,ollie314/lxd,ollie314/lxd,jsavikko/lxd,Skarlso/lxd,akshaykarle/lxd,basvanbeek/lxd,ericsnowcurrently/lxd,dvbportal/osx-lxd,lxc/lxd,jensg-st/lxd,georghopp/lxd,hallyn/lxd,lxc/lxd,akshaykarle/lxd,hallyn/lxd,tych0/lxd,akshaykarle/lxd,achanda/lxd,Malizor/lxd,dustinkirkland/lxd,lxc/lxd,rrva/lxd,hallyn/lxd,jumpstarter-io/lxd,smoser/lxd,dvbportal/osx-lxd,ollie314/lxd,dvbportal/osx-lxd,basvanbeek/lxd,atxwebs/lxd,Skarlso/lxd,georghopp/lxd,Skarlso/lxd,hallyn/lxd,basvanbeek/lxd,yura-pakhuchiy/lxd,achanda/lxd,techtonik/lxd,sl1pm4t/lxd,tych0/lxd,atxwebs/lxd,mjeanson/lxd,stgraber/lxd,dustinkirkland/lxd,tych0/lxd,jensg-st/lxd,rcj4747/lxd,stgraber/lxd