Do not instantiate multiple DocumentBuilderFactories

We're instantiating builders themsenves, so we can safely reuse a single
factory. No sense in initiating it more than once.

Change-Id: I70dfa2d5cc51a09722bb7ad41ce4d61f8691ac3d
Signed-off-by: Robert Varga <rovarga@cisco.com>
Merge "Do not instantiate multiple DocumentBuilderFactories"