[build] fix configure.ac in release tarball
[build] fix configure.ac in release tarball

only mingle with configure.ac if configure.ac-t exists

Signed-off-by: Fabio M. Di Nitto <510df3d038b805d3c95a0d349043a42f16d04605@redhat.com>

kgaillot/libqb,kgaillot/libqb,ClusterLabs/libqb,ClusterLabs/libqb,kgaillot/libqb,ClusterLabs/libqb