standardize pep8 jobs for mw extensions (+pyflakes)

The git scm macro arenow relying on $ZUUL_PROJECT instead of
gerrit-name. This way the extensions jobs can rely on the standard job
template '{name}-pep8'.

The diff is:

--- output-prev/mwext-WikimediaMaintenance-pep8	2013-08-29
17:14:39.000000000 +0200
+++ output/mwext-WikimediaMaintenance-pep8	2013-08-29
17:57:23.000000000 +0200
@@ -10 +10,2 @@
-  <canRoam>true</canRoam>
+  <assignedNode>hasContintPackages</assignedNode>
+  <canRoam>false</canRoam>
@@ -101 +102 @@
-        <url>/srv/ssd/zuul/git/mediawiki/extensions/WikimediaMaintenance</url>
+        <url>/srv/ssd/zuul/git/$ZUUL_PROJECT</url>
@@ -121 +122 @@
-    <relativeTargetDir>extensions/WikimediaMaintenance</relativeTargetDir>
+    <relativeTargetDir/>

There is no need to fetch the extension under /extensions/ since we are
not going to run any code but just lint it.

Jobs updated:

mwext-BlameMaps-pep8
mwext-ConfirmEdit-pep8
mwext-DumpHTML-pep8
mwext-EventLogging-pep8
mwext-Offline-pep8
mwext-OpenStackManager-pep8
mwext-SemanticBundle-pep8
mwext-SemanticResultFormats-pep8
mwext-WikimediaMaintenance-pep8

Since I have applied the 'python-jobs' job group, this patch also adds
pyflakes jobs:

mwext-BlameMaps-pyflakes
mwext-ConfirmEdit-pyflakes
mwext-DumpHTML-pyflakes
mwext-EventLogging-pyflakes
mwext-Offline-pyflakes
mwext-OpenStackManager-pyflakes
mwext-SemanticBundle-pyflakes
mwext-SemanticResultFormats-pyflakes
mwext-WikimediaMaintenance-pyflakes

Change-Id: Id378e258e4aa65fa457c5c169f8240f0e71c8a97