KnoxCLI needs to print usage when alias not provided

This needs to fail gracefully.
/usr/hdp/current/knox-server/bin/knoxcli.sh create-alias
java.lang.ArrayIndexOutOfBoundsException: 1
at org.apache.hadoop.gateway.util.KnoxCLI.init(KnoxCLI.java:154)
at org.apache.hadoop.gateway.util.KnoxCLI.run(KnoxCLI.java:88)
at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:70)
at org.apache.hadoop.gateway.util.KnoxCLI.main(KnoxCLI.java:649)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.hadoop.gateway.launcher.Invoker.invokeMainMethod(Invoker.java:70)
at org.apache.hadoop.gateway.launcher.Invoker.invoke(Invoker.java:39)
at org.apache.hadoop.gateway.launcher.Command.run(Command.java:101)
at org.apache.hadoop.gateway.launcher.Launcher.run(Launcher.java:69)
at org.apache.hadoop.gateway.launcher.Launcher.main(Launcher.java:46)