zdtm.py: Wait for tasks to die more
zdtm.py: Wait for tasks to die more

On loaded jenkins nodes sometimes it takes much more than 4 seconds.

Signed-off-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@parallels.com>

tych0/criu,KKoukiou/criu-remote,AuthenticEshkinKot/criu,fbocharov/criu,wtf42/criu,efiop/criu,svloyso/criu,fbocharov/criu,svloyso/criu,wtf42/criu,svloyso/criu,tych0/criu,ldu4/criu,ldu4/criu,ldu4/criu,fbocharov/criu,AuthenticEshkinKot/criu,wtf42/criu,tych0/criu,KKoukiou/criu-remote,eabatalov/criu,svloyso/criu,eabatalov/criu,KKoukiou/criu-remote,efiop/criu,wtf42/criu,ldu4/criu,AuthenticEshkinKot/criu,AuthenticEshkinKot/criu,wtf42/criu,efiop/criu,AuthenticEshkinKot/criu,KKoukiou/criu-remote,efiop/criu,ldu4/criu,ldu4/criu,fbocharov/criu,fbocharov/criu,KKoukiou/criu-remote,eabatalov/criu,wtf42/criu,svloyso/criu,efiop/criu,fbocharov/criu,KKoukiou/criu-remote,tych0/criu,eabatalov/criu,efiop/criu,tych0/criu,eabatalov/criu,eabatalov/criu,svloyso/criu,AuthenticEshkinKot/criu,tych0/criu