ewaol-tests/bats: Bump to v1.6.1

This also reverts commit 12197648 since it includes the fix for
https://github.com/bats-core/bats-core/issues/575



Issue-Id: SCM-4394
Signed-off-by: Diego Sueiro <diego.sueiro@arm.com>
Change-Id: I976e95c9487a1110fcc11a702b0d9b0fb0789c2b