Add a test to reproduce a deadlock when the queue size is small
Add a test to reproduce a deadlock when the queue size is small

When the buffer size of the incoming channel is 10, the test fails
with the following deadlock issue:

1) maybeSplitRangesByConfigs() acquires the mutex lock.
2) maybeSplitRangesByConfigs() blocks since the channel is full.
3) the split queue won't finish processing the range since the range
   split never finishes.

Here are stacktraces of goruntines from the test failure:

goroutine 245 [chan send]:
github.com/cockroachdb/cockroach/storage.(*baseQueue).MaybeAdd(0xc20805e900, 0xc208186510, 0x0, 0x809, 0x0, 0x0, 0x0)
     /Users/kaneda/Development/go/src/github.com/cockroachdb/cockroach/storage/queue.go:177 +0x4b0
github.com/cockroachdb/cockroach/storage.(*Store).maybeSplitRangesByConfigs(0xc2080a4000, 0xc208070a00, 0x1f, 0x20)
     /Users/kaneda/Development/go/src/github.com/cockroachdb/cockroach/storage/store.go:679 +0x284
github.com/cockroachdb/cockroach/storage.(*Store).configGossipUpdate(0xc2080a4000, 0x4abb2d0, 0xa, 0xc208022301)
     /Users/kaneda/Development/go/src/github.com/cockroachdb/cockroach/storage/store.go:640 +0x302

goroutine 20 [semacquire]:
sync.(*Mutex).Lock(0xc2080a4138)
     /usr/local/go/src/sync/mutex.go:66 +0xd3
sync.(*RWMutex).Lock(0xc2080a4138)
     /usr/local/go/src/sync/rwmutex.go:82 +0x33
github.com/cockroachdb/cockroach/storage.(*Store).GroupStorage(0xc2080a4000, 0x1, 0x0, 0x0)
     /Users/kaneda/Development/go/src/github.com/cockroachdb/cockroach/storage/store.go:1437 +0x56
github.com/cockroachdb/cockroach/multiraft.func·008()
     /Users/kaneda/Development/go/src/github.com/cockroachdb/cockroach/multiraft/storage.go:157 +0x3ac

goroutine 23 [chan send]:
github.com/cockroachdb/cockroach/multiraft.(*MultiRaft).SubmitCommand(0xc20809e180, 0x19, 0xc20815e4b0, 0x10, 0xc20827cc40, 0xdc, 0xdc, 0xc20811dc80)
    /Users/kaneda/Development/go/src/github.com/cockroachdb/cockroach/multiraft/multiraft.go:333 +0x3d0
   ...
github.com/cockroachdb/cockroach/client.runOne(0x5715520, 0xc2080400c8, 0xc208244c00, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
    /Users/kaneda/Development/go/src/github.com/cockroachdb/cockroach/client/db.go:900 +0x6b
github.com/cockroachdb/cockroach/client.(*DB).AdminSplit(0xc2080400c8, 0x4a369c0, 0xc208285360, 0x4a369c0, 0xc208285380, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
    /Users/kaneda/Development/go/src/github.com/cockroachdb/cockroach/client/db.go:287 +0xfb
github.com/cockroachdb/cockroach/storage.(*splitQueue).process(0xc208020d60, 0x0, 0x716, 0x0, 0x0, 0x0, 0xc208130e10, 0x0, 0x0)
    /Users/kaneda/Development/go/src/github.com/cockroachdb/cockroach/storage/split_queue.go:92 +0x32c
github.com/cockroachdb/cockroach/storage.(*baseQueue).processOne(0xc20805e900, 0xc208076000, 0xc20805e480)
    /Users/kaneda/Development/go/src/github.com/cockroachdb/cockroach/storage/queue.go:261 +0x4dc
github.com/cockroachdb/cockroach/storage.func·013()
    /Users/kaneda/Development/go/src/github.com/cockroachdb/cockroach/storage/queue.go:214 +0x14b

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