Load the whole certificate chain.
Load the whole certificate chain.

Proxies generated with MyProxy can have a really long chain. We
need to load the whole certificate chain so that it can be properly
validated and the VOMS info correctlty extracted.

Closes #1

IFCA/keystone-voms,enolfc/keystone-voms,enolfc/keystone-voms,alvarolopez/keystone-voms