Add linux_errno to resolv_stats_test_utils

Also do the revelant change in resolv_unit_test
to give the default value to linux_errno.

Bug: 150662964
Bug: 151166599
Test: atest
Merged-In: Ia5a4e509ad8728a18f9a8a9c7b9d74059e2e307f
Change-Id: I57d280efcd353076faa4dcb7f0c5bda337693dc9
(cherry picked from commit 7543ff11)