info-provider: fix works-by-accent bug when importing dCache config

The info-provider uses XML Entities to import dCache configuration.
The xmllint documentation, a used to work around a limitation in
Xerces, describes how a command-line option is required for it to
honour such Entity imports; however, earlier versions of xmllint did
not enforce this restriction and the info-provider worked despite
mistakenly omitting this option.

Mitigation against CVE-2014-0191 was achieved by fixing xmllint, so
enforcing the documented behaviour.  This change broke info-provider
with the following error being displayed:

/usr/share/dcache/info-provider/glue-both.xml:35: parser error : Entity 'dcache.paths.etc' not defined

This patch adds the option to tell xmllint to honour Entity imports.

Target: master
Request: 2.9
Request: 2.8
Request: 2.7
Request: 2.6
Request: 2.2