Changed how ruby versions are selected again

.travis.yml

@@ -4,6 +4,8 @@ before_install:
   - sudo apt-get update -qq
   - sudo apt-get install -qq libgtest-dev libgflags-dev python-virtualenv
 script:
+  - rvm install 2.1.2
+  - rvm use 2.1.2
   - ./tools/run_tests/run_tests.py -l c -t -j 16 -c dbg -s 2.0
   - ./tools/run_tests/run_tests.py -l c++ -t -j 16 -c dbg -s 2.0
   - make clean

tools/run_tests/build_ruby.sh

@@ -31,9 +31,6 @@
 
 set -ex
 
-rvm install 2.1.2
-rvm use 2.1.2
-
 CONFIG=${CONFIG:-opt}
 
 # change to grpc repo root

tools/run_tests/run_ruby.sh

@@ -30,8 +30,6 @@
 
 set -ex
 
-rvm use 2.1.2
-
 # change to grpc repo root
 cd $(dirname $0)/../../src/ruby