Catch common runtime errors in chutney shell scripts

Let's gradually convert our scripts to use:

set -e
set -u
set -o pipefail

And maybe:

IFS=$'\n\t'

These settings help catch common errors in bash scripts at runtime: http://redsymbol.net/articles/unofficial-bash-strict-mode/

(Shellcheck helps us catch errors while writing scripts, but it can't help with runtime failures.)

Follow-up to legacy/trac#33451 (moved).