Fetch account info from LDAP if session email address not exist

[Jiang Xin]

To make less LDAP query, we only do ldap bind and query if page is redirect from CoSign SSO page.

But what if user login from CoSign SSO first, and visit trac latter. At this circumstance, no redirect occur, and user email address not set by default.

[Jiang Xin]

(In [5275]) > To make less LDAP query, we only do ldap bind and query

if page is redirect from CoSign? SSO page. But what if user login from CoSign? SSO first, and visit trac latter. At this circumstance, no redirect occur, and user email address not set by default.

Fixed #4636: It can be easily workaround: Simply test if the user email address has already set or not.