use "use" with icon defs, rather than redefining each time

based on
https://groups.google.com/forum/?fromgroups=#!topic/d3-js/EtEwgOYnY6U

better performance
avoids the chrome caching issues
remove debug
tidying
copy management subnet info if relevant
nx-os interface labels
tidy
different ids based on ios derivative
tidy
explicitly set mgmt interface label for xr and nx-os
tidy management ips