.zshrc: Change npm test logic

The whole `if command ...` logic doesn't make sense to me, because
the command exits with 0 if it is successful, which means false!

This is just more readable anyways.

Signed-off-by: Alan Orth <alan.orth@gmail.com>

.zshrc

@@ -43,7 +43,8 @@ export ANSIBLE_HOSTS=hosts
 # if we have npm, we probably want to use npm binaries
 # I don't like installing globally (npm -g), so add local
 # node modules' bin to PATH
-if which npm >/dev/null 2>&1; then
+command -v npm >/dev/null 2>&1
+if [[ $? -eq 0 ]]; then
     export PATH=$PATH:node_modules/.bin
 fi