Fix multiple drag scroll intervals being registered
Fix multiple drag scroll intervals being registered

Tyriar/xterm.js,sourcelair/xterm.js,Tyriar/xterm.js,xtermjs/xterm.js,xtermjs/xterm.js,Tyriar/xterm.js,akalipetis/xterm.js,sourcelair/xterm.js,akalipetis/xterm.js,Tyriar/xterm.js,xtermjs/xterm.js,akalipetis/xterm.js,xtermjs/xterm.js,sourcelair/xterm.js,xtermjs/xterm.js,akalipetis/xterm.js,sourcelair/xterm.js,Tyriar/xterm.js