Some test script fixes

packages/grpc-js/scripts/xds.sh

@@ -1,7 +1,5 @@
 #!/bin/bash
 
-nvm use 12
-
 set -exu -o pipefail
 [[ -f /VERSION ]] && cat /VERSION
 
@@ -11,14 +9,8 @@ base=$(pwd)
 npm run compile
 
 cd ../../..
-branch=$(git branch --all --no-color --contains "${KOKORO_GITHUB_COMMIT}" \
-    | grep -v HEAD | head -1)
-shopt -s extglob
-branch="${branch//[[:space:]]}"
-branch="${branch##remotes/origin/}"
-shopt -u extglob
 
-git clone -b "${branch}" --single-branch --depth=1 https://github.com/grpc/grpc.git
+git clone -b remotes/origin/ --single-branch --depth=1 https://github.com/grpc/grpc.git
 
 grpc/tools/run_tests/helper_scripts/prep_xds.sh
 

run-tests.sh

@@ -77,6 +77,9 @@ done
 
 if [ "$OS" = "Linux" ]
 then
+  set +ex
+  nvm use 12
+  set -ex
   # Run the xds interop tests only on Linux
   ./packages/grpc-js/scripts/xds.sh
 fi