[TESTS] Improve script robustness (#2893)

[TESTS] Improve script robustness (#2893)

A number of test scripts use the '|| exit 1' idiom.  This has two
issues, first process exit codes are defined to be in the range 0-255.
Second, more importantly, the idiom is fragile because it requires
that every possible failure point be explicitly coded.  This patch
removes the idiom in favour of "set -e" as used in the docker scripts
as a more robust mechanism to ensure that script failures are always
caught and propagated by default.