Fix lock between soffice and some convert tests

Running org.nuxeo.ecm.platform.convert.tests.TestWPD2TextConverter
Sep 04, 2014 6:49:47 AM org.artofsolving.jodconverter.office.ProcessPoolOfficeManager <init>
INFO: ProcessManager implementation is WindowsProcessManager
06:49:48,024 WARN  [OOoManagerComponent] OpenOffice was not found, JOD Converter won't be available: a process with acceptString 'socket,host=127.0.0.1,port=2002' is already running; pid 1904
06:49:48,039 WARN  [CommandLineExecutorComponent] Command not available: wpd2text (command wpd2text not found in system path. You need to install wpd2text (deb: libwpd-tools)  http://libwpd.sourceforge.net/download.html)
Skipping Wordperfect conversion test since libpwd-tool is not installed converter check output : You need to install wpd2text (deb: libwpd-tools)  http://libwpd.sourceforge.net/download.html converter check output : command wpd2text not found in system pathTests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.34 sec