BUG/MINOR: stick-table/cli: Check for invalid ipv4 key

BUG/MINOR: stick-table/cli: Check for invalid ipv4 key

When an ipv4 key is used to filter a CLI command on a stick table
clear/set/show table ...), inetaddr_host+htonl combination was used
with no error checking.

Instead, we now use inet_pton(), which is what we use for ipv6 addresses
since b7c962b0c0 ("BUG/MINOR: stick-table/cli: Check for invalid ipv6 key")

Doing this allows us to easily check for parsing errors: we're trading off
some parsing efficience to better catch input errors and ensure we get
similar behavior between ipv4 and ipv6 addresses handling.

This patch may be backported to all supported versions.