Revert "Removed explicit setting of df.discard_subset_failing_expectations to true"
Revert "Removed explicit setting of df.discard_subset_failing_expectations to true"

This reverts commit 8a5481bf1c2dbd0b51a1422036c4bc7d299bd6d0.

great-expectations/great_expectations,great-expectations/great_expectations,great-expectations/great_expectations,great-expectations/great_expectations