Use upgrade flag to prevent global node modules from being removed

src/freedombone-utils-nodejs

     $mesh_install_nodejs_prefix wget https://deb.nodesource.com/gpgkey/nodesource.gpg.key -O /root/node.gpg.key
     if [ ! -f "$rootdir/root/node.gpg.key" ]; then
         echo $'Unable to obtain gpg key for nodejs repo'
+        NODE_UPGRADE=
         exit 6389252
     fi
     $mesh_install_nodejs_prefix apt-key add /root/node.gpg.key
     $mesh_install_nodejs_prefix apt-get update
     $mesh_install_nodejs_prefix apt-get -yq remove --purge nodejs
 
-    if [ -d "$rootdir/usr/local/lib/node_modules" ]; then
-        rm -rf "$rootdir/usr/local/lib/node_modules"
+    if [ ! $NODE_UPGRADE ]; then
+        if [ -d "$rootdir/usr/local/lib/node_modules" ]; then
+            rm -rf "$rootdir/usr/local/lib/node_modules"
+        fi
     fi
+
     if [ -f "$rootdir/usr/local/bin/node" ]; then
         rm "$rootdir/usr/local/bin/node"
     fi
         if [ ! -f "${rootdir}/usr/local/bin/node" ]; then
             if [ ! -f "${rootdir}/usr/bin/nodejs" ]; then
                 echo $'nodejs was not installed'
+                NODE_UPGRADE=
                 exit 63962
             fi
         fi
 
     if [ ! -f "$rootdir/usr/bin/node" ]; then
         echo $'/usr/bin/node not found'
+        NODE_UPGRADE=
         exit 7235728
     fi
 
     chmod +x "$rootdir/usr/bin/test_nodejs_install"
     if ! $mesh_install_nodejs_prefix /usr/bin/test_nodejs_install; then
         echo $"nodejs version numbers did not match. Architecture is $NPM_ARCH."
+        NODE_UPGRADE=
         exit 76835282
     fi
     rm "$rootdir/usr/bin/test_nodejs_install"
+    NODE_UPGRADE=
 }
 
 function nodejs_upgrade {
     fi
     read_config_param ARCHITECTURE
     get_npm_arch
+    NODE_UPGRADE=1
     rootdir=
     mesh_install_nodejs
 }