Now info command takes a table of sub info commands,
and changed do_info() to do_info_help() to do help funtion
only.
 Note that now "info <unknown-topic>" returns error instead
of list of info topics.

Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>