src/grd: replace fetch-gerrit-patch.sh

As discussed with Neels, replace the previous version of the script that
didn't work anymore (probably due to api change from gerrit) with a new
one that works with the current api and also doesn't require unlocking
the ssh key.

Change-Id: Ie5d061323dce6843cafe49434250cc4780c8c832
diff --git a/.gitignore b/.gitignore
index 3b70a48..6aa1dd0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,8 +5,8 @@
 make-*
 make/*
 src/*
-!src/fetch-gerrit-patch.sh
 !src/gits
+!src/grd
 !src/osmo-add-gerrit-hooks.sh
 !src/README
 net/*