New user from SSO cause duplicate registration

[TomasKulhanek]

Initiated probably by duplicate call of createUserSSO.

Server reports

Apr 25 09:29:51 instance-1 westlife-repository: org.springframework.web.util.NestedServletException: Request processing failed; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement
...
Apr 25 09:29:51 instance-1 westlife-repository: Caused by:
Apr 25 09:29:51 instance-1 westlife-repository: org.hibernate.exception.ConstraintViolationException: could not execute statement
Apr 25 09:29:51 instance-1 westlife-repository: at org.hibernate.exception.internal.SQLExceptionTypeDelegate.convert(SQLExceptionTypeDelegate.java:72)
...
Apr 25 09:29:51 instance-1 westlife-repository: at com.sun.proxy.$Proxy67.saveUser(Unknown Source)
Apr 25 09:29:51 instance-1 westlife-repository: at org.cirmmp.spring.controller.SharedCon.createSSOUser(SharedCon.java:73)
Apr 25 09:29:51 instance-1 westlife-repository: at org.cirmmp.spring.controller.SharedCon.checkAuthentication(SharedCon.java:128)
Apr 25 09:29:51 instance-1 westlife-repository: at org.cirmmp.spring.controller.DatasetServiceCon.listDataset(DatasetServiceCon.java:103)