CRM-14472 - query correct table for contribution-type vs. event-type PCPs

When returning getPCPList(), query correct table for contribution-type vs. event-type PCPs. This allows a backend user to credit a contribution to an event PCP when using Contributions > New Contribution.

----------------------------------------
* CRM-14472: Credit offline contribution to an event PCP
  https://issues.civicrm.org/jira/browse/CRM-14472