net: app: client: set remote port after DNS lookup

In net_app_init_client(), the remote port is set after an initial
set of checks based on the remote_addr's assigned family.

However, if the peer_addr_str is a host name which needs to be
resolved via DNS, the family won't be set yet, and the port is
left as 0.

To fix this behavior let's move the port assignment after the
DNS lookup section to be sure that the remote sa_family is set.

Signed-off-by: Michael Scott <michael@opensourcefoundries.com>