ovs-ofctl.at: Prevent msys from getting confused with ipv6 address.

ovs-ofctl.at: Prevent msys from getting confused with ipv6 address.

msys has a set of rules which triggers an automatic conversion of
arguments into something else to suit Windows requirements. Sometimes
this also causes unwanted conversions. Details of the rules is here:
http://www.mingw.org/wiki/Posix_path_conversion

msys converts ::1/::1 into ;1\;1. To prevent this, use fullform
ipv6 address of the form 0:0:0:0:0:0:0:1 instead.

Signed-off-by: Gurucharan Shetty <gshetty@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>