Fix "search_cert" API method (searching by ISSUER_DN)
Fix "search_cert" API method (searching by ISSUER_DN)

Also removes code for attribute EMAIL which does not exist anymore.

stefanomarty/openxpki,oliwel/openxpki,aleibl/openxpki,stefanomarty/openxpki,aleibl/openxpki,aleibl/openxpki,oliwel/openxpki,openxpki/openxpki,openxpki/openxpki,aleibl/openxpki,oliwel/openxpki,oliwel/openxpki,openxpki/openxpki,oliwel/openxpki,oliwel/openxpki,aleibl/openxpki,aleibl/openxpki,stefanomarty/openxpki,stefanomarty/openxpki,openxpki/openxpki,stefanomarty/openxpki,stefanomarty/openxpki