Make cms and lms tests run independently (they had been colliding on collectstatic)

rakefile

@@ -27,7 +27,7 @@ NORMALIZED_DEPLOY_NAME = DEPLOY_NAME.downcase().gsub(/[_\/]/, '-')
 INSTALL_DIR_PATH = File.join(DEPLOY_DIR, NORMALIZED_DEPLOY_NAME)
 PIP_REPO_REQUIREMENTS = "#{INSTALL_DIR_PATH}/repo-requirements.txt"
 # Set up the clean and clobber tasks
-CLOBBER.include(BUILD_DIR, REPORT_DIR, 'cover*', '.coverage', 'test_root/*_repo')
+CLOBBER.include(BUILD_DIR, REPORT_DIR, 'cover*', '.coverage', 'test_root/*_repo', 'test_root/staticfiles')
 CLEAN.include("#{BUILD_DIR}/*.deb", "#{BUILD_DIR}/util")
 
 def select_executable(*cmds)
@@ -54,6 +54,10 @@ task :predjango do
     sh('git submodule update --init')
 end
 
+task :clean_test_files do
+    sh("git clean -fdx test_root")
+end
+
 [:lms, :cms, :common].each do |system|
     report_dir = File.join(REPORT_DIR, system.to_s)
     directory report_dir
@@ -93,7 +97,7 @@ end
 
     # Per System tasks
     desc "Run all django tests on our djangoapps for the #{system}"
-    task "test_#{system}" => ["#{system}:collectstatic:test", "fasttest_#{system}"]
+    task "test_#{system}" => ["clean_test_files", "#{system}:collectstatic:test", "fasttest_#{system}"]
 
     # Have a way to run the tests without running collectstatic -- useful when debugging without
     # messing with static files.