netfilter: xt_conntrack: fix inverted conntrack direction test

--ctdir ORIGINAL matches REPLY packets, and vv:

userspace sets "invert_flags &= ~XT_CONNTRACK_DIRECTION" in ORIGINAL
case.

Thus: (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) ^
      !!(info->invert_flags & XT_CONNTRACK_DIRECTION))

yields "1 ^ 0", which is true -> returns false.

Reproducer:
iptables -I OUTPUT 1 -p tcp --syn -m conntrack --ctdir ORIGINAL

Signed-off-by: Florian Westphal <fwestphal@astaro.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>