devmode-test: check more python versions

We had a bug where /usr/local/bin/python worked but /usr/bin/python
failed.  Expand the sanity check to include all the known prefixes.

BUG=chromium:1000719
TEST=`./devinstall_test.py betty ./chromiumos_test_image.bin` passes

Change-Id: I3222b9e49477456473a02d382b8d95e31e584ecf
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crostestutils/+/1838655
Reviewed-by: Achuith Bhandarkar <achuith@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
1 file changed