Fixed race condition for TCP link deleting.
Fixed race condition for TCP link deleting.

This could have caused crashes when a client disconnected from the server.

ionux/MCServer,linnemannr/MCServer,Haxi52/cuberite,marvinkopf/cuberite,Schwertspize/cuberite,mjssw/cuberite,ionux/MCServer,linnemannr/MCServer,Haxi52/cuberite,mc-server/MCServer,electromatter/cuberite,Haxi52/cuberite,kevinr/cuberite,Howaner/MCServer,nevercast/cuberite,nicodinh/cuberite,nevercast/cuberite,nounoursheureux/MCServer,birkett/cuberite,nounoursheureux/MCServer,birkett/MCServer,thetaeo/cuberite,Schwertspize/cuberite,HelenaKitty/EbooMC,mjssw/cuberite,mjssw/cuberite,QUSpilPrgm/cuberite,bendl/cuberite,tonibm19/cuberite,HelenaKitty/EbooMC,Altenius/cuberite,Fighter19/cuberite,thetaeo/cuberite,jammet/MCServer,nounoursheureux/MCServer,linnemannr/MCServer,electromatter/cuberite,ionux/MCServer,Altenius/cuberite,QUSpilPrgm/cuberite,mmdk95/cuberite,Schwertspize/cuberite,ionux/MCServer,birkett/MCServer,mmdk95/cuberite,kevinr/cuberite,bendl/cuberite,guijun/MCServer,mmdk95/cuberite,guijun/MCServer,birkett/MCServer,marvinkopf/cuberite,Tri125/MCServer,electromatter/cuberite,nounoursheureux/MCServer,birkett/cuberite,nounoursheureux/MCServer,HelenaKitty/EbooMC,johnsoch/cuberite,mmdk95/cuberite,linnemannr/MCServer,jammet/MCServer,kevinr/cuberite,Fighter19/cuberite,Haxi52/cuberite,nevercast/cuberite,SamOatesPlugins/cuberite,johnsoch/cuberite,SamOatesPlugins/cuberite,nichwall/cuberite,bendl/cuberite,zackp30/cuberite,thetaeo/cuberite,nicodinh/cuberite,marvinkopf/cuberite,zackp30/cuberite,QUSpilPrgm/cuberite,Howaner/MCServer,Fighter19/cuberite,birkett/MCServer,SamOatesPlugins/cuberite,birkett/cuberite,Schwertspize/cuberite,jammet/MCServer,birkett/cuberite,nevercast/cuberite,Schwertspize/cuberite,QUSpilPrgm/cuberite,mmdk95/cuberite,zackp30/cuberite,mc-server/MCServer,SamOatesPlugins/cuberite,marvinkopf/cuberite,linnemannr/MCServer,kevinr/cuberite,Howaner/MCServer,guijun/MCServer,mc-server/MCServer,marvinkopf/cuberite,Howaner/MCServer,mc-server/MCServer,tonibm19/cuberite,Frownigami1/cuberite,birkett/cuberite,bendl/cuberite,marvinkopf/cuberite,ionux/MCServer,QUSpilPrgm/cuberite,Altenius/cuberite,tonibm19/cuberite,electromatter/cuberite,linnemannr/MCServer,birkett/MCServer,mc-server/MCServer,mjssw/cuberite,tonibm19/cuberite,birkett/cuberite,nicodinh/cuberite,Fighter19/cuberite,nicodinh/cuberite,nevercast/cuberite,zackp30/cuberite,thetaeo/cuberite,Howaner/MCServer,Tri125/MCServer,johnsoch/cuberite,HelenaKitty/EbooMC,mmdk95/cuberite,SamOatesPlugins/cuberite,nicodinh/cuberite,Tri125/MCServer,Frownigami1/cuberite,Frownigami1/cuberite,electromatter/cuberite,Tri125/MCServer,guijun/MCServer,electromatter/cuberite,kevinr/cuberite,Howaner/MCServer,Haxi52/cuberite,Tri125/MCServer,tonibm19/cuberite,ionux/MCServer,thetaeo/cuberite,nicodinh/cuberite,QUSpilPrgm/cuberite,nichwall/cuberite,mjssw/cuberite,tonibm19/cuberite,nichwall/cuberite,guijun/MCServer,HelenaKitty/EbooMC,Frownigami1/cuberite,zackp30/cuberite,thetaeo/cuberite,Altenius/cuberite,mjssw/cuberite,nichwall/cuberite,mc-server/MCServer,birkett/MCServer,Altenius/cuberite,Haxi52/cuberite,jammet/MCServer,johnsoch/cuberite,nevercast/cuberite,Frownigami1/cuberite,bendl/cuberite,jammet/MCServer,kevinr/cuberite,Tri125/MCServer,zackp30/cuberite,nichwall/cuberite,johnsoch/cuberite,Fighter19/cuberite,nounoursheureux/MCServer,Fighter19/cuberite,nichwall/cuberite,guijun/MCServer,jammet/MCServer