COLO-compare: Rename compare function and remove duplicate codes

Rename colo_packet_compare() to colo_packet_compare_common() that
make tcp_compare udp_compare icmp_compare reuse this function.
Remove minimum packet size check in icmp_compare, because we have
check this in parse_packet_early().

Signed-off-by: Zhang Chen <zhangchen.fnst@cn.fujitsu.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
