Revert "- reset retry counter on 404 answer for all python 2.7.x versions"

This reverts commit 320238350fb5c0026f9538e8bb48de3b155dfab4.
With python >= 2.7.1 this codepath should not be needed (see also
https://hg.python.org/cpython/rev/64287).

Conflicts:
	osc/conf.py
Revert "Fix condition for using urllib2 workaround"

This reverts commit 2f14cedcff96d7991c97604b94717f1c927c5d4e.

Actually, this was meant to fix https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=762825,
which was (probably) caused due to the following:
- commit 320238350fb5c0026f9538e8bb48de3b155dfab4 introduced a codepath, which
  should not be needed for python >= 2.7.1 (see also
  https://hg.python.org/cpython/rev/64287)
- this codepath uses the "reset_retry_count" method, which is not present in
  Debian Jessie's libpython2.7-stdlib: libpython2.7-stdlib_2.7.8-11 backports
  a patch from python's 2.7.9 branch, which removes the "reset_retry_count"
  method (https://hg.python.org/cpython/rev/c1edc4e43eb1).

This fixes bnc#911080 and github issue #131.