ss: Make leading ":" always optional for sport and dport

ss: Make leading ":" always optional for sport and dport

The sport and dport conditions in expressions were inconsistent on
whether there should be a ":" at the beginning of the port when only a
port was provided depending on the family. The link and netlink
families required a ":" to work. The vsock family required the ":"
to be absent. The inet and inet6 families work with or without a leading
":".

This makes the leading ":" optional in all cases, so if sport or dport
are used, then it works with a leading ":" or without one, as inet and
inet6 did.

Signed-off-by: Thayne McCombs <astrothayne@gmail.com>
Signed-off-by: David Ahern <dsahern@kernel.org>