Cleanup ruby repo dir before clonning it

Really old repo could produce a lot of errors

Change-Id: I804e280fb4349544b7019d036936a145c0b2d1ec
diff --git a/src/com/mirantis/mk/Ruby.groovy b/src/com/mirantis/mk/Ruby.groovy
index 2e1e494..1a093e5 100644
--- a/src/com/mirantis/mk/Ruby.groovy
+++ b/src/com/mirantis/mk/Ruby.groovy
@@ -11,7 +11,8 @@
 def ensureRubyEnv(rubyVersion="2.6.6"){
     if (!fileExists("/var/lib/jenkins/.rbenv/versions/${rubyVersion}/bin/ruby")){
         //XXX: patch ruby-build because debian package is quite old
-        sh "git clone https://github.com/rbenv/ruby-build.git ~/.rbenv/plugins/ruby-build || git -C ~/.rbenv/plugins/ruby-build pull origin master"
+        sh "rm -rf ~/.rbenv/plugins/ruby-build"
+        sh "git clone https://github.com/rbenv/ruby-build.git ~/.rbenv/plugins/ruby-build"
         sh "rbenv install ${rubyVersion} -sv";
     }
     sh "rbenv local ${rubyVersion};rbenv exec gem update --system"