container.go: fix spelling of docker option to `ps`
container.go: fix spelling of docker option to `ps`

--quit should be --quiet

the net effect was to break crane rm:  the exists() call would return
false, so crane would never rm the container.  Similarly for start

rmoorman/crane,tmc/crane,stajkowski/crane,ghbliu/crane,dreamcat4/crane,michaelsauter/crane,dreamcat4/crane,inthroxify/crane,inthroxify/crane,t-suwa/crane,tmc/crane,rmoorman/crane,stajkowski/crane,jesper/crane,ghbliu/crane,bjaglin/crane,jesper/crane,ScientificRevenue/crane,michaelsauter/crane,t-suwa/crane,bjaglin/crane