Revert " channelz: stage 4 - add security and socket option info"

[lyuxuan]

Reverts #2098

Appengine will fail with the error below:

go-app-builder: Failed parsing input: parser: bad import "syscall" in google.golang.org/grpc/channelz/funcs.go from GOPATH

The root cause of it is in type_linux.go.

grpc-go/channelz/types_linux.go

Lines 21 to 25 in 629f6bc

	import (
	"syscall"
	"golang.org/x/sys/unix"
	)