Added python-requests to nailgun.spec

There is also fuel-web patch which adds
requests to nailgun/requirements.txt

fuel-web patch: I73db9cd7724291dc57904834d38dbe9afb371462

Change-Id: I280de416af0079da1976ab37112dbf8764ef2839
Closes-Bug: 1393859
Merge "Added python-requests to nailgun.spec"