resolv: Fix file handle leak in __resolv_conf_load [BZ #25429]

res_vinit_1 did not close the stream on errors, only on success.
This change moves closing the stream to __resolv_conf_load, for both
the success and error cases.

Fixes commit 89f187a4 ("resolv: Use
getline for configuration file reading in res_vinit_1") and commit
3f853f22 ("resolv: Lift domain search
list limits [BZ #19569] [BZ #21475]"), where memory allocation was
introduced into res_vinit_1.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>