This deadlocks in the case that we have an external process
communicating with LibreOffice as the SolarMutexReleaser allows a
connection to be processed while the normal code has just released the
SolarMutex. If the external call code now goes down the same code path
we deadlock on the SolarMutex together with other mutexes in the
clipboard code.

Change-Id: I18fd6953c9566452a31b1a4c32c68494ec7a52ac
Reviewed-on: https://gerrit.libreoffice.org/27251Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>