SUSE: Clean up libxslt/libxml2 related dependencies

libxml2-devel is a dependency of libxslt-devel, so we don't need
to explicitly include it. Also, since it is only really needed
by python-lxml, consolidate it into devlibs and remove the copies.
Also remove a non-existing package reference along the way

Change-Id: If9afaaa93f2c485baa1efff74d7ae58c59713de6

Author: dirkmueller

files/rpms-suse/devlibs

@@ -1,6 +1,5 @@
 libffi-devel  # pyOpenSSL
 libopenssl-devel  # pyOpenSSL
-libxml2-devel  # lxml
 libxslt-devel  # lxml
 postgresql-devel  # psycopg2
 libmysqlclient-devel # MySQL-python

files/rpms-suse/glance

@@ -1,2 +1 @@
-libxml2-devel
 python-devel