openmpi-nightly-tarball.sh: go to "verbose" instead of "debug"

Now that the Coverity submit seems to be working, dial back the
cron-generated output to "verbose" instead of "debug".

contrib/build-server/openmpi-nightly-tarball.sh

@@ -120,7 +120,7 @@ for tarball in `cat $pending_coverity`; do
     $HOME/scripts/openmpi-nightly-coverity.pl \
         --filename=$tarball \
         --coverity-token=`cat $HOME/coverity-token.txt` \
-        --debug \
+        --verbose \
         --logfile-dir=$HOME/coverity \
         --make-args=-j8 \
         --configure-args="--enable-mpi-fortran --enable-mpi-java --enable-oshmem --enable-oshmem-fortran --enable-oshmem-java --with-mxm=/opt/mellanox/mxm --with-psm --with-usnic"