DO NOT MERGE Fix use-after-free of mClient member DnsProxyListener::GetHostByNameHandler::run().

Found by ASan.

Test: Flash ASan build, boot up and verify that system/netd does not
crash with AddressSanitizer induced errors.

Bug: 32810214
Bug: 29748723

(cherry picked from commit f8bb7ecc)

Change-Id: I8814756588b2bb4c78583a829e08d33305797642