client cannot connect to non-existing namespaces
Fix splice arguments and `socket.rooms` value update in `socket.leaveAll`.

Hat tip @Marreck
Merge pull request #1700 from rase-/fix/rooms

Fix splice arguments and `socket.rooms` value update in `socket.leaveAll`
Merge pull request #1688 from fdellabetta/server_side_namespace

client cannot connect to non-existing namespaces