The Crowd2 jenkins plugin with version 2.8 has an option 'Restrict groups', allowing multiple groups seperated by commas. But it does not work when group name has preceding or trailing blanks.

How to reproduce:

1. Jenkins -> Configure Global Security -> Access Control -> Crowd 2
   fill Restrict groups with
   "jenkins-users, jenkins-job-managers , jenkins-administrators"
2. Login in Crowd console, create three groups of jenkins-users, jenkins-job-managers and jenkins-administrators, add users in the groups.
3. Login in Jenkins, users in group jenkins-users will succeed, but not that in group jenkins-job-managers and jenkins-administrators.
4. Change Restrict groups to 'jenkins-users,jenkins-job-managers,jenkins-administrators' and all users would login in successfully.

Since Crowd does not allow creating groups with blanks in group name, the Crowd2 plugin may safely ignore blanks in the Restrict group parameter.