Ensure enabling local symbols doesn't change the module hash (aws#2169)

### Description of changes:
The original intention of aws#1005 was to
ensure break-kat.go always worked with the library.
aws#1252 then used a side effect to get
the module hash but didn't actually fail the build if the hash was
different.

Turn on `pipefail` so the script exits unsuccessfully if any command
fails even in a pipe. Previously if test-break-kat.sh failed the script
didn't exit, instead it would continue to the grep which would also fail
to find any matching string, and then the `|| true` ensured the script
always continued on.

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under the terms of the Apache 2.0 license and the ISC license.