Rewrite calls to Proxy.getPreferredHttpHost

Use java.net.URLConnection which is the only maintained method of
making http requests from java.

These were the last calls to getPreferredHttpHost and that hidden
API will now be deleted.

Change-Id: I97e022507ba656f627754af4e889f4812314ea90
Import translations. DO NOT MERGE

Change-Id: I97f50623444c023b843cc615ac252944bfc3ceca
Auto-generated-cl: translation import