rvm use is not necessary

tools/jenkins/docker_run_tests.sh

@@ -38,16 +38,11 @@ export ASAN_SYMBOLIZER_PATH=/usr/bin/llvm-symbolizer-3.5
 
 # Ensure that programs depending on current-user-ownership of cache directories
 # are satisfied (it's being mounted from outside the image).
-chown `whoami` $XDG_CACHE_HOME
+chown $(whoami) $XDG_CACHE_HOME
 
 mkdir -p /var/local/git
 git clone --recursive /var/local/jenkins/grpc /var/local/git/grpc
 
-if [ -x "$(command -v rvm)" ]
-then
-  rvm use ruby-2.1
-fi
-
 mkdir -p reports
 
 exit_code=0