tox.ini: install eobuilder not as a dependency

tox.ini

@@ -23,12 +23,11 @@ commands =
 
 [testenv:package]
 # eobuilder is not on pypi, too bad
-install_command = pip install --pre --find-links https://jenkins.entrouvert.org/packages/ {opts} {packages}
 deps = setuptools
   pip<8
-  eobuilder
   pyasn1
   ndg-httpsclient
   pyopenssl
 commands =
+  pip install -U --find-links https://jenkins.entrouvert.org/packages/ eobuilder
   sh -c "sudo -u eobuilder -E env HOME=/var/lib/eobuilder PATH=$PATH $VIRTUAL_ENV/bin/eobuilder-ctl -d wheezy,jessie `pwd`"