cleanup interop test scripts

tools/dockerfile/grpc_interop_node/build_interop.sh

@@ -41,8 +41,6 @@ cd /var/local/git/grpc
 nvm use 0.12
 nvm alias default 0.12  # prevent the need to run 'nvm use' in every shell
 
-make install-certs
-
 # build Node interop client & server
 npm install -g node-gyp
 npm install --unsafe-perm --build-from-source

tools/dockerfile/grpc_interop_ruby/build_interop.sh

@@ -40,7 +40,5 @@ cp -r /var/local/jenkins/service_account $HOME || true
 cd /var/local/git/grpc
 rvm --default use ruby-2.1
 
-make install-certs
-
 # build Ruby interop client and server
 (cd src/ruby && gem update bundler && bundle && rake compile)