Don't exit just because we think there was a possible deadlock (#21342)

changelog/21342.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+core: Don't exit just because we think there's a potential deadlock.
+```

command/server.go

@@ -63,6 +63,7 @@ import (
 	"github.com/mitchellh/go-testing-interface"
 	"github.com/pkg/errors"
 	"github.com/posener/complete"
+	"github.com/sasha-s/go-deadlock"
 	"go.uber.org/atomic"
 	"golang.org/x/net/http/httpproxy"
 	"google.golang.org/grpc/grpclog"
@@ -1001,6 +1002,9 @@ func (c *ServerCommand) Run(args []string) int {
 		return 1
 	}
 
+	// Don't exit just because we saw a potential deadlock.
+	deadlock.Opts.OnPotentialDeadlock = func() {}
+
 	c.logGate = gatedwriter.NewWriter(os.Stderr)
 	c.logWriter = c.logGate