move rspec / selenium stages to root level

refs DE-338

Nospot removal requires all non-build stages to not be wrapped in the protectedNode() function.

Test Plan:
1. RSpec / Selenium stages pass
2. Build Summary Report works correctly

Change-Id: I313b865c1e2758177446905b62a5c7c6f1ed1830
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/262748
Reviewed-by: Kyle Rosenbaum <krosenbaum@instructure.com>
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
QA-Review: Aaron Ogata <aogata@instructure.com>
Product-Review: Aaron Ogata <aogata@instructure.com>

Jenkinsfile

@@ -360,6 +360,8 @@ pipeline {
                       if(env.GERRIT_PROJECT != "canvas-lms") {
                         sh "rm -vrf $LOCAL_WORKDIR@tmp"
                       }
+
+                      distribution.stashBuildScripts()
                     }
 
                   extendedStage('Rebase')
@@ -409,11 +411,6 @@ pipeline {
                       .required(configuration.isChangeMerged())
                       .queue(stages, { dependencyCheckStage() })
 
-                    distribution.stashBuildScripts()
-
-                    distribution.addRSpecSuites(stages)
-                    distribution.addSeleniumSuites(stages)
-
                     parallel(stages)
                   }
                 }
@@ -492,6 +489,9 @@ pipeline {
                     string(name: 'POSTGRES_IMAGE_TAG', value: "${env.POSTGRES_IMAGE_TAG}"),
                   ])
 
+                distribution.addRSpecSuites(nestedStages)
+                distribution.addSeleniumSuites(nestedStages)
+
                 parallel(nestedStages)
               }