Set loglevel = error for `Npm.depends`-related `npm` commands.

tools/isobuild/meteor-npm-userconfig

@@ -1,2 +1,7 @@
# This file intentionally left empty to ensure consistent npm
# configuration.
# These configuration options govern `npm` commands run on behalf of
# Meteor packages that have `Npm.depends` calls in their package.js files,
# not `meteor npm ...` commands. Because the developer is not running
# these commands herself, we don't care as much about helpful warnings,
# and we certainly don't want them to obscure actual errors.

loglevel = error