GetFunctionAttribute command is throwing an Anonymouse User Exception

When trying to execute a function from a client, we sometimes would get this exception. This is because GetFunctionAttribute is regarded as an internal message, so it's not getting the subject bound to the executing thread, but the cmdExecute method of this command is checking for authorization. Need to remove that check and update the docs to not include this client command.

[error 2017/01/12 15:25:20.968567 Pacific Standard Time mmartell-Win10:3084 7460] Region::GET_FUNCTION_ATTRIBUTES: An exception (org.apache.geode.security.GemFireSecurityException: Error: Anonymous User
at org.apache.geode.internal.security.IntegratedSecurityService.getSubject(IntegratedSecurityService.java:114)
at org.apache.geode.internal.security.IntegratedSecurityService.authorize(IntegratedSecurityService.java:273)
at org.apache.geode.internal.security.IntegratedSecurityService.authorize(IntegratedSecurityService.java:269)
at org.apache.geode.internal.security.IntegratedSecurityService.authorize(IntegratedSecurityService.java:264)
at org.apache.geode.internal.security.IntegratedSecurityService.authorize(IntegratedSecurityService.java:260)
at org.apache.geode.internal.security.IntegratedSecurityService.authorizeClusterRead(IntegratedSecurityService.java:220)
at org.apache.geode.internal.cache.tier.sockets.command.GetFunctionAttribute.cmdExecute(GetFunctionAttribute.java:60)
at org.apache.geode.internal.cache.tier.sockets.BaseCommand.execute(BaseCommand.java:141)
at org.apache.geode.internal.cache.tier.sockets.ServerConnection.doNormalMsg(ServerConnection.java:776)
at org.apache.geode.internal.cache.tier.sockets.ServerConnection.doOneMessage(ServerConnection.java:904)
at org.apache.geode.internal.cache.tier.sockets.ServerConnection.run(ServerConnection.java:1160)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at org.apache.geode.internal.cache.tier.sockets.AcceptorImpl$1$1.run(AcceptorImpl.java:519)
at java.lang.Thread.run(Thread.java:745)