The buildLowLevelConnection() will try to modify the read-only storage
and throw IOException.

Change-Id: I9b8ec840bebcac3c8a69bc6921d32e692d9d9e86
Reviewed-on: https://gerrit.libreoffice.org/67027
Tested-by: Jenkins
Reviewed-by: Michael Stahl <Michael.Stahl@cib.de>