[ upstream commit 5d20ca7e8322268320ee37096e19b8c7563e6a6f ]

Ensure that the allocation CIDR is non-nil and verify that the required
nodeAddressing requirements are fulfilled. Fixes the following panic:

```
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x259ebf1]

goroutine 1 [running]:
github.com/cilium/cilium/pkg/datapath/linux.(*linuxNodeHandler).createNodeRoute(0xc00017d650, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
        /go/src/github.com/cilium/cilium/pkg/datapath/linux/node.go:292 +0x71
github.com/cilium/cilium/pkg/datapath/linux.(*linuxNodeHandler).lookupNodeRoute(0xc00017d650, 0x0, 0xc0004804e0, 0x10, 0x10)
        /go/src/github.com/cilium/cilium/pkg/datapath/linux/node.go:309 +0x50
github.com/cilium/cilium/pkg/datapath/linux.(*linuxNodeHandler).nodeUpdate(0xc00017d650, 0x0, 0xc000e94c60, 0x0, 0x4adf920)
        /go/src/github.com/cilium/cilium/pkg/datapath/linux/node.go:456 +0x4b8
github.com/cilium/cilium/pkg/datapath/linux.(*linuxNodeHandler).NodeConfigurationChanged(0xc00017d650, 0x5dc, 0x5aa, 0x0, 0x4adf920, 0x0, 0x0, 0x10000000100, 0x0, 0x0)
        /go/src/github.com/cilium/cilium/pkg/datapath/linux/node.go:622 +0x1e1
main.(*Daemon).compileBase(0xc0007be700, 0x0, 0x0)
        /go/src/github.com/cilium/cilium/daemon/daemon.go:533 +0x7a9
main.(*Daemon).init(0xc0007be700, 0xc000e332b8, 0x1)
        /go/src/github.com/cilium/cilium/daemon/daemon.go:675 +0x126
main.NewDaemon(0x2f49b80, 0xc0004c8de0, 0x1, 0x1, 0xc00088f928, 0x113d542)
        /go/src/github.com/cilium/cilium/daemon/daemon.go:1191 +0x1177
main.runDaemon()
        /go/src/github.com/cilium/cilium/daemon/daemon_main.go:1062 +0x214
main.glob..func1(0x44ee920, 0xc0007e67d0, 0x0, 0x5)
        /go/src/github.com/cilium/cilium/daemon/daemon_main.go:108 +0x30
github.com/cilium/cilium/vendor/github.com/spf13/cobra.(*Command).execute(0x44ee920, 0xc00004c1f0, 0x5, 0x5, 0x44ee920, 0xc00004c1f0)
        /go/src/github.com/cilium/cilium/vendor/github.com/spf13/cobra/command.go:766 +0x2cc
github.com/cilium/cilium/vendor/github.com/spf13/cobra.(*Command).ExecuteC(0x44ee920, 0x2f2caf0, 0x2f543c0, 0x2f2cb10)
        /go/src/github.com/cilium/cilium/vendor/github.com/spf13/cobra/command.go:852 +0x2fd
github.com/cilium/cilium/vendor/github.com/spf13/cobra.(*Command).Execute(0x44ee920, 0x0, 0x0)
        /go/src/github.com/cilium/cilium/vendor/github.com/spf13/cobra/command.go:800 +0x2b
main.daemonMain()
        /go/src/github.com/cilium/cilium/daemon/daemon_main.go:126 +0x14c
main.main()
        /go/src/github.com/cilium/cilium/daemon/main.go:30 +0xc9
```

Signed-off-by: Thomas Graf <thomas@cilium.io>
Signed-off-by: Joe Stringer <joe@cilium.io>