Change vm.ip -esxcli to wait for ip

Similar to vm.ip (tools), the -esxcli option waits until the VM has a
valid ip address.  Unlike the tools option, -esxcli needs to poll.
Collapse whitespace in assert_line helper

This helper is often used against Go's tabwriter output,
where number of spaces may vary.
Explicit exit status check in assert_failure

Check that exit status is 1.  A go panic for example would result in
an exit status of 2.  We should never panic.
Include esxcli method info in response

The Hints include info about the esxcli method output, such as formatter
type (table, simple), human readable field names and units.
Add table formatter to esxcli command