...and make sure that the generated name is actually short enough to be stored
in a sockaddr_un::sun_path.  (oslPipeImpl::m_Name is only used to store such a
name, to be used in osl_closePipe, so just make it of the same size to guarantee
that copying between the two with strcpy will always work.)

Change-Id: I6d1d0c5518e6d09eff129d682a1a334d12201e90
Reviewed-on: https://gerrit.libreoffice.org/66469
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>