Fix https://issues.infn.it/jira/browse/VOMS-456
More checks on incoming cert chains
Fixed indentation.
Fixes verificationtime issue.

Commit 8ed971b34b8288baf933079b9a4e29060799c350 introduced an issue
that lead to failures in recognizing valid VOMS attributes in client
requests.

Now verificationtime is set for OpenSSL verification only if it
was actually set by the caller.

This commit improves error reporting in APIs.
Merge pull request #10 from italiangrid/fix/VOMS-456

Fix/voms 456