Modernize sources list for containerized package manager

installJRMC

@@ -434,16 +434,13 @@ get_latest_mc_version() {
   # Use generalized containerized package manager to determine latest MC version
   if install_package --silent buildah && 
   cnt=$(buildah from --quiet alpine:edge 2>/dev/null) &&
-  buildah run "$cnt" -- sh -c \
-    "apk add apt &>/dev/null &&
-    cat <<-EOF > /etc/apt/sources.list.d/jriver.sources
-			Types: deb
-			URIs: https://dist.jriver.com/latest/mediacenter/
-			Suites: $1
-			Components: main
-		EOF ;
-    cat /etc/apt/sources.list.d/jriver.sources ;
-    apt update --allow-insecure-repositories" &&
+  buildah run "$cnt" -- sh -c "apk add apt &>/dev/null && tee /etc/apt/sources.list.d/jriver.sources <<EOF
+Types: deb
+URIs: https://dist.jriver.com/latest/mediacenter/
+Suites: $1
+Components: main
+EOF
+&& apt update --allow-insecure-repositories" &&
   MC_VERSION=$(buildah run "$cnt" -- apt-cache policy mediacenter?? | grep Candidate | awk '{print $2}' | sort -V | tail -n1) &>/dev/null &&
   [[ $MC_VERSION =~ ^[0-9]+\.[0-9]+\.[0-9]+ ]]; then
     mc_version_source="containerized package manager"