tests: socket: Free resources with freeaddrinfo

In Zephyr this has no effect because getaddrinfo() returns a pointer
to a static array, but Coverity scan checks for this pattern.

Coverity-CID: 185273
Coverity-CID: 185279

Fixes #7085
Fixes #7091

Signed-off-by: Stig Bjørlykke <stig.bjorlykke@nordicsemi.no>