Avoid find_by_id given an id with alphanumeric in ParticipantController

When using the p_id to find the participant on the participants page, if the beginning of the id contains an integer it will truncate the rest of the p_id and search using the integer.
Example..

1. requesting /participants/044_abc
2. participants page found for participant with id 44, not p_id 044_abc

Ticket is https://code.bioinformatics.northwestern.edu/issues/issues/show/4397