There is a SolarMutexReleaser in the call chain so that using an own
mutex can deadlock.

Change-Id: I1dd0b0c78ce6cf436a470319e616099cb947b6e0
Reviewed-on: https://gerrit.libreoffice.org/27085Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>