"AttributeError: 'Element' object has no attribute 'getparent'" if lxml is not installed

Got this traceback upon running `bcfg2` on a fresh Precise install using the testing PPA (`bcfg2 1.3.0rc1 on Python 2.7.3`):

    Traceback (most recent call last):
      File "/usr/sbin/bcfg2", line 29, in <module>
        sys.exit(main())
      File "/usr/sbin/bcfg2", line 26, in main
        return Client(setup).run()
      File "/usr/lib/pymodules/python2.7/Bcfg2/Client/Client.py", line 307, in run
        self.tools.Execute()
      File "/usr/lib/pymodules/python2.7/Bcfg2/Client/Frame.py", line 499, in Execute
        self.InstallImportant()
      File "/usr/lib/pymodules/python2.7/Bcfg2/Client/Frame.py", line 236, in InstallImportant
        parent = cfile.getparent()
    AttributeError: 'Element' object has no attribute 'getparent'

Arises because of this check:

    parent = cfile.getparent()
    if ((parent.tag == "Bundle" and
         ((self.setup['bundle'] and
           parent.get("name") not in self.setup['bundle']) or
          (self.setup['skipbundle'] and
           parent.get("name") in self.setup['skipbundle']))) or
        (parent.tag == "Independent" and
         (self.setup['bundle'] or self.setup['skipindep']))):
        continue

However, `getparent()` only works if you have `lxml.etree` installed—`xml.etree` in the Python standard library (the fallback include) doesn't support this method.

Not confident enough in my understanding of what this code is doing to offer a patch, but hopefully it's a pretty straightforward fix.