Add apt dependencies for ceilometer tests

The ceilometer tests use an in-memory version of
MongoDB that uses spidermonkey for JavaScript
interpretation. spidermonkey, in turn, depends
on nspr and pkg-config.

Ceilometer also uses lxml, which wants libxml2-dev
and libxslt-dev.

bug 1115332

Change-Id: Ie2fca1203107b6397fa6babbef37dbaae7592373
Signed-off-by: Doug Hellmann <doug.hellmann@dreamhost.com>
Merge "Add apt dependencies for ceilometer tests"