WFLY-4084, add a regex to command completer to deal with multiple slashes in user input

https://issues.jboss.org/browse/WFLY-4084
Handle multiple slashes in the end of command for Tab press ([domain@localhost:9990 /] /host=master// It will display content under 'master' instead of root '/' ) 
This can't be done here. The command line parser should identify the problem and the tab-completion should not suggest anything. The proposed change will break intentional use of sequence /+ , for example :some-op(arg=a///b)