do not log password
This is trickier than it may first appear. We can't just filter the
password from os.Args, since that would require recreating the flag
parsing logic, which allows flags to be specified in a wide variety of
formats. And there is no API for calling that logic either.

So instead we log the results of the flag parsing, eliding the
password, and using a straight golang map for formatting (so we don't
have to get creative).
Assign iface parameter from defined variable.
Merge pull request #283 from rade/275_do_not_log_password

Closes #275
Merge remote-tracking branch 'upstream/master' into if_param

Conflicts:
	weave
	weaver/Dockerfile
Merge pull request #288 from viirya/if_param

Assign iface parameter from defined variable
install docker-ns in test VMs
handy for debugging