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 '/' ) 
I was not aware of sequence /+ use case. This therefore is not an adequate approach.
About tab "suggestion", in fedora terminal shell usage, it suggests somethings when command ends with more than one slash:
[wangchao@dhcp-16-223 wildfly-core]$ cd cli//
.settings/ src/       target/    
[wangchao@dhcp-16-223 wildfly-core]$ cd cli//src///
main/ test/ 
[wangchao@dhcp-16-223 wildfly-core]$ cd cli//src///
[wangchao@dhcp-16-223 src]$ pwd
/home/wangchao/work/jboss/wildfly/wildfly-core/cli/src

3.267 Pathname in http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap03.html#tag_03_267 also describes that "Multiple successive <slash> characters are considered to be the same as one <slash>"