use npm scripts arg passing instead of $KARMAFLAGS to make cross-compat

jenkins.sh

@@ -2,7 +2,6 @@
 
 set -e
 
-export KARMAFLAGS="--no-colors"
 export NVM_DIR="$HOME/.nvm"
 [ -s "$NVM_DIR/nvm.sh" ] && . "$NVM_DIR/nvm.sh"
 nvm use 4
@@ -16,7 +15,7 @@ npm install
 (cd node_modules/matrix-js-sdk && npm install)
 
 # run the mocha tests
-npm run test
+npm run test -- --no-colors
 
 # run eslint
 npm run lintall -- -f checkstyle -o eslint.xml || true