Agent should go crash if installation of essential flows failed

[weiqiangt]

Describe the bug
The AntreaAgent keeps running even it met flow installation errors. For E.g. AntreaProxy needs kernel version ≥ 4.6 and thus in the lower version kernel any flow installation with ct(nat) will fail which leads to several key flows in table 30 not exist. The AntreaAgent should crash instead of keeping running which misleads users.

To Reproduce
Deploy Antrea on Node with kernel version lower than 4.6. There is no flow in table 30.

Expected
The Agent should crash if any essential flow can not be installed.

Actual behavior
The Agent keeps running.

Additional context
#1652

[weiqiangt]

In github.com/contiv/lib!openflow@v0.0.0-20201014051314-c1702744526c/util/stream.go:71

	go m.outbound()
	go m.inbound()
	for i := 0; i < numParserGoroutines; i++ {
		go m.parse()
	}

There are multiple parsers that make messages lose the order, and thus we see that the BundleClose message may be received earlier than BundleAddErrorMesage.

[github-actions]

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