connect: correctly number ipv6 network adapter

connect: correctly number ipv6 network adapter

In ba50532, the variable 'cnt' was added to both the IPv6 and the
IPv4 version of git_tcp_connect_sock, intended to identify which
network adapter the connection failed on. But in the IPv6 version,
the variable was never increased, leaving it constantly at zero.

This behaviour isn't very useful, so let's fix it by increasing
the variable at every loop-iteration.

Signed-off-by: Erik Faye-Lund <redacted>
Signed-off-by: Junio C Hamano <redacted>