Revert "minor fix, CRM-12970"

This reverts commit a8ec0901625fd3c2d6c4199ab547af3420a82945.
Revert "fixes to setdefaults, CRM-12970"

This reverts commit 66094995512afa0a8c37f0a0b5304ce394ec6bb1.
--CRM-12970, fixed for more than one event discount set

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* CRM-12970: civicrm_price_field_value not removed for discount price set
  http://issues.civicrm.org/jira/browse/CRM-12970
Merge pull request #1640 from pradpnayak/CRM-12970

Crm 12970
Still one edge case that breaks the discount grid, but this is an improvement.