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
Merge "Just reset the repo instead of trying to co files"