Fix gossip-stalled deadlock
Fix gossip-stalled deadlock

The `stalled` channel is used to indicate that gossip has stalled; it
is useless to place more than one "stalled" message on it.
This commit reduces the buffer size of `stalled` to 1 and never
changes the sending behaviour to never block.

Fixes #1341.
Fixes #1342.
Fixes #1343.

GokulSrinivas/cockroach,cuongdo/cockroach,linearb/cockroach,nkhuyu/cockroach,slavau/cockroach,veteranlu/cockroach,nkhuyu/cockroach,abhishekgahlot/cockroach,glycerine/cockroach,bg451/cockroach,mbonaci/cockroach,alex/cockroach,loucash/cockroach,vaibhavarora/cockroach,cuongdo/cockroach,c4pt0r/cockroach,paperstreet/cockroach,freakynit/cockroach,c4pt0r/cockroach,arjun4084346/cockroach,XisiHuang/cockroach,paperstreet/cockroach,glycerine/cockroach,nieyy/cockroach,freakynit/cockroach,GokulSrinivas/cockroach,maxlang/cockroach,cockroachdb/cockroach,maxlang/cockroach,cuongdo/cockroach,freakynit/cockroach,linearb/cockroach,arjun4084346/cockroach,fengshao0907/cockroach,arypurnomoz/cockroach,mbonaci/cockroach,freakynit/cockroach,petermattis/cockroach,jamesgraves/cockroach,ajayaa/cockroach,jgautheron/cockroach,yiixiansheng/cockroach,maxlang/cockroach,cuongdo/cockroach,petermattis/cockroach,marcuswestin/cockroach,linearb/cockroach,paperstreet/cockroach,abhishekgahlot/cockroach,ajayaa/cockroach,jess-edwards/cockroach,bg451/cockroach,linearb/cockroach,yosiat/cockroach,yiixiansheng/cockroach,fengshao0907/cockroach,jamesgraves/cockroach,cockroachdb/cockroach,slavau/cockroach,cockroachdb/cockroach,mbonaci/cockroach,c4pt0r/cockroach,loucash/cockroach,jess-edwards/cockroach,hassyma/cockroach,bg451/cockroach,alunarbeach/cockroach,marcuswestin/cockroach,mbertschler/cockroach,briceburg/cockroach,vivekmenezes/cockroach,SustainFund/cockroach,slavau/cockroach,cuongdo/cockroach,cockroachdb/cockroach,il9ue/cockroach,yiixiansheng/cockroach,mbertschler/cockroach,vivekmenezes/cockroach,jamesgraves/cockroach,il9ue/cockroach,maxlang/cockroach,bg451/cockroach,loucash/cockroach,linearb/cockroach,jamesgraves/cockroach,arypurnomoz/cockroach,marcuswestin/cockroach,arjun4084346/cockroach,marcuswestin/cockroach,jess-edwards/cockroach,petermattis/cockroach,sunya123/cockroach,briceburg/cockroach,sunya123/cockroach,nieyy/cockroach,paperstreet/cockroach,arjun4084346/cockroach,cockroachdb/cockroach,arjun4084346/cockroach,ajayaa/cockroach,SustainFund/cockroach,cuongdo/cockroach,linearb/cockroach,arjun4084346/cockroach,veteranlu/cockroach,alunarbeach/cockroach,marcuswestin/cockroach,fengshao0907/cockroach,yiixiansheng/cockroach,jgautheron/cockroach,loucash/cockroach,nieyy/cockroach,alex/cockroach,jmank88/cockroach,SustainFund/cockroach,cockroachdb/cockroach,petermattis/cockroach,il9ue/cockroach,arjun4084346/cockroach,veteranlu/cockroach,il9ue/cockroach,abhishekgahlot/cockroach,jess-edwards/cockroach,glycerine/cockroach,il9ue/cockroach,jmank88/cockroach,XisiHuang/cockroach,veteranlu/cockroach,alunarbeach/cockroach,arypurnomoz/cockroach,SustainFund/cockroach,loucash/cockroach,alunarbeach/cockroach,jgautheron/cockroach,mbonaci/cockroach,jmank88/cockroach,alunarbeach/cockroach,veteranlu/cockroach,yosiat/cockroach,marcuswestin/cockroach,yosiat/cockroach,vivekmenezes/cockroach,bg451/cockroach,jmank88/cockroach,jess-edwards/cockroach,jmank88/cockroach,XisiHuang/cockroach,vaibhavarora/cockroach,nieyy/cockroach,vaibhavarora/cockroach,jgautheron/cockroach,nkhuyu/cockroach,petermattis/cockroach,paperstreet/cockroach,yiixiansheng/cockroach,Abioy/cockroach,Abioy/cockroach,veteranlu/cockroach,marcuswestin/cockroach,paperstreet/cockroach,vivekmenezes/cockroach,chrisseto/cockroach,jess-edwards/cockroach,mbertschler/cockroach,ajayaa/cockroach,arypurnomoz/cockroach,briceburg/cockroach,mbertschler/cockroach,bg451/cockroach,jgautheron/cockroach,vivekmenezes/cockroach,vivekmenezes/cockroach,maxlang/cockroach,XisiHuang/cockroach,jamesgraves/cockroach,c4pt0r/cockroach,nieyy/cockroach,paperstreet/cockroach,Abioy/cockroach,jmank88/cockroach,nkhuyu/cockroach,petermattis/cockroach,hassyma/cockroach,petermattis/cockroach,alunarbeach/cockroach,cockroachdb/cockroach,fengshao0907/cockroach,Abioy/cockroach,bg451/cockroach,vivekmenezes/cockroach,sunya123/cockroach,yosiat/cockroach,hassyma/cockroach,paperstreet/cockroach,arypurnomoz/cockroach,vaibhavarora/cockroach,Abioy/cockroach,slavau/cockroach,sunya123/cockroach,abhishekgahlot/cockroach,slavau/cockroach,glycerine/cockroach,glycerine/cockroach,mbertschler/cockroach,ajayaa/cockroach,briceburg/cockroach,nieyy/cockroach,briceburg/cockroach,arypurnomoz/cockroach,hassyma/cockroach,chrisseto/cockroach,glycerine/cockroach,hassyma/cockroach,ajayaa/cockroach,hassyma/cockroach,vivekmenezes/cockroach,marcuswestin/cockroach,abhishekgahlot/cockroach,alex/cockroach,briceburg/cockroach,veteranlu/cockroach,chrisseto/cockroach,jess-edwards/cockroach,slavau/cockroach,mbonaci/cockroach,sunya123/cockroach,nkhuyu/cockroach,vaibhavarora/cockroach,GokulSrinivas/cockroach,nkhuyu/cockroach,cuongdo/cockroach,jamesgraves/cockroach,linearb/cockroach,chrisseto/cockroach,glycerine/cockroach,abhishekgahlot/cockroach,c4pt0r/cockroach,jamesgraves/cockroach,chrisseto/cockroach,alex/cockroach,il9ue/cockroach,Abioy/cockroach,yosiat/cockroach,mbertschler/cockroach,vaibhavarora/cockroach,glycerine/cockroach,petermattis/cockroach,il9ue/cockroach,sunya123/cockroach,nieyy/cock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