Disable the merge half of TestTree.
Disable the merge half of TestTree.

Closes #2206.

arjun4084346/cockroach,sunya123/cockroach,jess-edwards/cockroach,bg451/cockroach,maxlang/cockroach,nieyy/cockroach,paperstreet/cockroach,arjun4084346/cockroach,veteranlu/cockroach,cuongdo/cockroach,petermattis/cockroach,glycerine/cockroach,petermattis/cockroach,petermattis/cockroach,glycerine/cockroach,jmank88/cockroach,glycerine/cockroach,il9ue/cockroach,bg451/cockroach,vaibhavarora/cockroach,vaibhavarora/cockroach,il9ue/cockroach,mbertschler/cockroach,cockroachdb/cockroach,veteranlu/cockroach,linearb/cockroach,linearb/cockroach,cockroachdb/cockroach,nieyy/cockroach,cuongdo/cockroach,cuongdo/cockroach,vivekmenezes/cockroach,bg451/cockroach,cockroachdb/cockroach,sunya123/cockroach,linearb/cockroach,bg451/cockroach,mbertschler/cockroach,marcuswestin/cockroach,cuongdo/cockroach,jess-edwards/cockroach,arjun4084346/cockroach,paperstreet/cockroach,vivekmenezes/cockroach,sunya123/cockroach,veteranlu/cockroach,arjun4084346/cockroach,sunya123/cockroach,sunya123/cockroach,linearb/cockroach,nieyy/cockroach,il9ue/cockroach,maxlang/cockroach,marcuswestin/cockroach,arjun4084346/cockroach,cockroachdb/cockroach,il9ue/cockroach,veteranlu/cockroach,vivekmenezes/cockroach,maxlang/cockroach,il9ue/cockroach,jamesgraves/cockroach,cuongdo/cockroach,paperstreet/cockroach,jmank88/cockroach,cuongdo/cockroach,vaibhavarora/cockroach,jess-edwards/cockroach,marcuswestin/cockroach,petermattis/cockroach,nieyy/cockroach,paperstreet/cockroach,vaibhavarora/cockroach,paperstreet/cockroach,marcuswestin/cockroach,sunya123/cockroach,petermattis/cockroach,jess-edwards/cockroach,veteranlu/cockroach,jamesgraves/cockroach,bg451/cockroach,maxlang/cockroach,bg451/cockroach,jess-edwards/cockroach,marcuswestin/cockroach,vaibhavarora/cockroach,glycerine/cockroach,jamesgraves/cockroach,nieyy/cockroach,vaibhavarora/cockroach,jmank88/cockroach,jamesgraves/cockroach,nieyy/cockroach,glycerine/cockroach,jmank88/cockroach,maxlang/cockroach,paperstreet/cockroach,jess-edwards/cockroach,veteranlu/cockroach,mbertschler/cockroach,arjun4084346/cockroach,sunya123/cockroach,jamesgraves/cockroach,paperstreet/cockroach,jmank88/cockroach,mbertschler/cockroach,vaibhavarora/cockroach,jamesgraves/cockroach,marcuswestin/cockroach,vivekmenezes/cockroach,jess-edwards/cockroach,vivekmenezes/cockroach,nieyy/cockroach,mbertschler/cockroach,marcuswestin/cockroach,maxlang/cockroach,il9ue/cockroach,jamesgraves/cockroach,cuongdo/cockroach,veteranlu/cockroach,arjun4084346/cockroach,vaibhavarora/cockroach,vivekmenezes/cockroach,il9ue/cockroach,marcuswestin/cockroach,linearb/cockroach,jmank88/cockroach,paperstreet/cockroach,nieyy/cockroach,vivekmenezes/cockroach,mbertschler/cockroach,cockroachdb/cockroach,maxlang/cockroach,veteranlu/cockroach,petermattis/cockroach,glycerine/cockroach,maxlang/cockroach,cuongdo/cockroach,vivekmenezes/cockroach,sunya123/cockroach,linearb/cockroach,petermattis/cockroach,linearb/cockroach,glycerine/cockroach,il9ue/cockroach,jmank88/cockroach,arjun4084346/cockroach,cockroachdb/cockroach,mbertschler/cockroach,cockroachdb/cockroach,glycerine/cockroach,bg451/cockroach,petermattis/cockroach,cockroachdb/cockroach