drtprod: export vars instead of passing every time

Release note: none.
Epic: none.

scripts/drtprod

@@ -4,6 +4,9 @@
 # clusters that ensures consistent use of the correct project-assignment vars
 # and done some additional sanity check enforcement on some flags.
 
+export GCE_PROJECT=cockroach-drt
+export ROACHPROD_DNS="drt.crdb.io"
+
 case $1 in
   "start")
     if [[ "$*" != *"--secure"* ]]; then
@@ -27,7 +30,7 @@ case $1 in
     shift
     cluster=$1
     set -euo pipefail
-    GCE_PROJECT=cockroach-drt roachprod adminurl $cluster --ips |
+    roachprod adminurl $cluster --ips |
       awk '{printf "%04d\t%s\n", NR, $0}' | # prepend the padded node IDs.
       sed -e 's,http://\(.*\):26258/,\1,g' | # remove the HTTP part.
       while read node ip; do
@@ -39,4 +42,4 @@ case $1 in
 esac
 
 
-GCE_PROJECT=cockroach-drt  ROACHPROD_DNS="drt.crdb.io" roachprod "$@"
+roachprod "$@"