crosh: Permit SSH-ing to IPv6 addresses.
crosh: Permit SSH-ing to IPv6 addresses.

Change-Id: I0d95c7fa317cb7f41db01ade26eb415319dc50b7

BUG=chromium-os:11211
TEST=tried it with ":1", "::1", various IPv4 and IPv6 addresses, hostnames, and bogus values

Review URL: http://codereview.chromium.org/6347023

joshfire/chromiumos-platform-window_manager,joshfire/chromiumos-platform-window_manager,joshfire/chromiumos-platform-window_manager,joshfire/chromiumos-platform-window_manager