DO NOT MERGE Remove "if (auto ret = " treated as unused by some compilers

It's not good form to have a variable that's created and used only once
in the same line anyway, so the compilers that flag it are probably in
the right.

Test: netd_benchmark
Bug: 29748723

(cherry picked from commit e65244b5)

Change-Id: I80b8c321087947c08d5d5b9cb6ca7b4987b2ac77