Revert "Travis add python-lvm2 dependency"

This reverts commit 7c02d991d0cb84abf092dc910772e8319df651d1.

python-lvm2 isn't available in trusty (used in Travis-CI)

.travis.yml

@@ -3,9 +3,6 @@ dist: trusty
 language: python
 python:
   - '2.7'
-before_install:
-  - sudo apt-get -qq update
-  - sudo apt-get install -y python-lvm2
 install:
   - pip install --quiet -r ci/requirements.txt
   - git clone https://github.com/"${TRAVIS_REPO_SLUG%%/*}"/qubes-builder ~/qubes-builder