Just reset the repo instead of trying to co files

We can just reset the repo instead of trying to checkout specific files.
This fix external repos which doesn't not have requirements.txt or
test-requirements.txt.

Closes-Bug: 1231334
Change-Id: Iab898f5e8a422cc0cbfe44839c938f22c7525fd8
diff --git a/functions b/functions
index d969677..92b4ee1 100644
--- a/functions
+++ b/functions
@@ -1257,7 +1257,7 @@
 
     # Undo requirements changes, if we made them
     if [ $update_requirements -eq 0 ]; then
-        (cd $project_dir && git checkout -- requirements.txt test-requirements.txt setup.py)
+         (cd $project_dir && git reset --hard)
     fi
 }