ncm-ceph: fix for SSH multiplexing when using old SSH version

supplies a fix for  #321 

using `no_controlpersist` self var is only solution without refactoring a lot of subs .. (`$gvalues` does not go deep enough)

EL6.6 will have an updated SSH version with support for `ControlPersist`
Use `qw` instead of list of string constants.