internal: fix onClose state transitions
When onClose occurs during WaitForHandshake, it should immediately
exit createTransport instead of leaving CONNECTING and entering READY.
Furthermore, when any onClose happens, the state should change to
TRANSIENT FAILURE.
Fixes#2340Fixes#2341
Also fixes an unreported bug in which entering READY causes a
Dial call to end prematurely, instead of blocking until a READY
transport is found.
Reverts grpc/grpc-go#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.
629f6bc5e5/channelz/types_linux.go (L21-L25)
This PR splits out grpclb from grpc. I have made the PR in several commits so you can see more clearly the steps that happened.
There are a few possibly contentious points that I would like to make clear up front:
* grpclb will no longer autoload as a load balancer. I think this is okay, as service config is not widely (at all?) used, and I believe this is the only way to access it.
* `internal` is used more, as a way of having code shared between packages without exposing types
* ConnectivityStateEvaluator, as used by grpclb, is no longer thread safe. I believe there is an outer mutex that guards access, but I want to point out this subtle change up here.
All but one tests pass with this, due to another cyclic dependency. I can fix this, but it is a little more widely scoped (such as exposing grpc.server and grpc.errorDesc in the internal package). This PR is a nearly-passing sample of that last step to get this working.
PTAL @menghanl @dfawley
Jean de Klerk
lyuxuan
dfawley
Carl Mastrangelo