__netbox: pass handling of requirements.txt to pip3

Previous handling passed a list of pip packages from the
requirements.txt via xargs to the pip install directly.

This is error-prone, as shown with the major 3 Netbox release. This type
breaks cause of comments inside of it. This commit fixes it, while
keeping the compatibility to install gnuicorn separate.

type/__netbox/gencode-remote

@@ -51,7 +51,9 @@ fi
 # Install python dependencies.
 #  avoid gunicorn, because it will be done in an other type
 grep -v "^gunicorn==" "\$tmpdir/$src/requirements.txt" \
-    | xargs /opt/netbox/venv/bin/pip3 install -q
+    > "\$tmpdir/$src/requirements.txt.new"
+/opt/netbox/venv/bin/pip3 install -q -r "\$tmpdir/$src/requirements.txt.new"
+
 EOF
 
     if [ -f "$__object/parameter/ldap-server" ]; then