url_downloader: remove pre-precise/squid 2 compat

Change-Id: I0c7a7d4a3143bda10ce0a8e7e96946a8997ab5a4
install-server: remove pre-precise/squid 2 compat

Change-Id: I867d8654c019b396835800be95bff2bfba5049da
Merge changes I867d8654,I0c7a7d4a into production

* changes:
  install-server: remove pre-precise/squid 2 compat
  url_downloader: remove pre-precise/squid 2 compat