WFLY-981 :  @RunAs/@RunAsPrincipal are ignored for @Startup/@Singleton bean

Adding a SecurityInterceptor for Singleton beans for postconstruct methods.
The security context on postcontruct methods in singleton is not propagating the security context.
JIRA : https://issues.jboss.org/browse/WFLY-981
BZ: https://bugzilla.redhat.com/show_bug.cgi?id=921723