Support cleanup of projects that are checked out to multiple paths.
Support cleanup of projects that are checked out to multiple paths.

Currently if the same project is checked out to multiple locations, we
may delete the project without deleting all the places that the project
is checked out. Fix that.

BUG=chromium:333044
TEST=All unit tests. Trybot run with official.xml manifest.

Change-Id: Ic6b481f20f74243d53ccd9258f9b65a488dfaf80
Reviewed-on: https://chromium-review.googlesource.com/182074
Reviewed-by: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>
Tested-by: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>
Commit-Queue: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>

chadversary/chromiumos.chromite,bpsinc-native/src_third_party_chromite,bpsinc-native/src_third_party_chromite,bpsinc-native/src_third_party_chromite,chadversary/chromiumos.chromite