Use upgrade rather than install

src/freedombone-utils-nodejs

@@ -113,7 +113,7 @@ function upgrade_nodejs {
     CURR_NPM_VERSION=$(npm --version)
     CURR_N_VERSION=$(n --version)
     if [[ "$CURR_NPM_VERSION" != "$NPM_VERSION" ]]; then
-        npm install -g npm@${NPM_VERSION} --save
+        npm upgrade -g npm@${NPM_VERSION} --save
     fi
     if [[ "$CURR_N_VERSION" != "$NODEJS_N_VERSION" ]]; then
         npm upgrade -g n@${NODEJS_N_VERSION} --save