Use concurrent maps in connection manager (fix #2723)
Use concurrent maps in connection manager (fix #2723)

tsmgeek/traccar,jon-stumpf/traccar,tsmgeek/traccar,tananaev/traccar,tananaev/traccar,stalien/traccar_test,jssenyange/traccar,ninioe/traccar,ninioe/traccar,5of9/traccar,5of9/traccar,vipien/traccar,jssenyange/traccar,AnshulJain1985/Roadcast-Tracker,jon-stumpf/traccar,al3x1s/traccar,orcoliver/traccar,renaudallard/traccar,tananaev/traccar,orcoliver/traccar,AnshulJain1985/Roadcast-Tracker,jssenyange/traccar,ninioe/traccar,vipien/traccar,jon-stumpf/traccar,renaudallard/traccar,al3x1s/traccar,stalien/traccar_test,orcoliver/traccar,tsmgeek/traccar