net: lwip: dns: Call env_set() from dns loop instead of found callback

net: lwip: dns: Call env_set() from dns loop instead of found callback

The lwIP dns command handle env_set() calls from the found callback and
printf() to console in the dns loop. Making it more complex than it
needs to be.

Simplify and ensure any environment variable that is being set is the
same value that would have been printed on console.

There should not be any intended change in behavior, besides the change
from using ip4addr helper to using version less ipaddr helper.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Jerome Forissier <jerome.forissier@arm.com>