Description of problem:
"-c CONTAINER" is not necessary for "oc attach"

Version-Release number of selected component (if applicable):
openshift v3.3.0.22

How reproducible:
Always

Steps to Reproduce:
1. # oc attach -h

Actual results:
1. # oc attach -h
<snip>
Usage:
  oc attach POD -c CONTAINER [options]
<snip>

Expected results:
Usage:
  oc attach POD [options]
or
  oc attach POD [-c CONTAINER] [options]

Additional info:
# oc rsh -h
Usage:
  oc rsh [options] POD [COMMAND]
Options:
  -c, --container='': Container name; defaults to first container

# oc exec -h
Usage:
  oc exec [options] POD [-c CONTAINER] -- COMMAND [args...]
Options:
  -c, --container='': Container name. If omitted, the first container in the pod will be chosen