Use downstream bootstrap-salt.sh

the upstream version recently dropped support for Ubuntu 16.04 since
it is EOL.

Related-Issue: PRODX-3456
Change-Id: I12bc558d5c1aea684c4b3dece765a5002492d705
(cherry picked from commit d67695267a204c02ca4c267620c952ab685f484e)
1 file changed