case insensitive matched userids do not map assigned roles

Per NEXUS-4115, Nexus needs to allow case insensitive userid matching.

There is a bug in nexus 3 LDAP user role mapping where this fails.

Create an LDAP configuration as in the attached screenshots and map an LDAP user with 'test0002' user id. Assign the user the nx-admin role.

You can successfully authenticate with this user as expected with test0002, TEST0002, or tEsT002, however the roles are not mapped correctly unless you use the exact case userid that was mapped `test0002`.

This results in being able to signin into the UI using any case, but not seeing the Administration cog or getting any admin privileges unless using an exact case match to test0002.

Expected

Correctly map all roles to a successfully authenticated user.