[Investigation] Add lifecycle test

[titpetric]

This adds an aggresive test against the gateway test lifecycle. It concurrently starts and stops an unbounded amount of gateway test servers and attempts to exit the test after 5 seconds with a dumb time.Sleep. It starts about 20K of them on my local and triggers many data races / panics due to various reasons like global state.

Fixed a data race:

• cli.Init is invoked in each test, as it holds global app state, overwrites needlessly
• testutil: defaultTestConfig / reset config (incorrect test usage? see fixed test)

Questions:

1. Should we remove cli.Init from Tests? It should not be triggered from test scope perhaps. At least once should be enough to maintain behaviour and pass race checks.
2. Investigate additional issues reported and propose fixes

Test with:

cd tests/lifecycle
task services:up
go test -v -race ./...

Left in draft to consider wider effort. The ideal outcome is us being able to parallelize all tests.

Remaining races detected:

     41       /root/tyk/tyk/gateway/testutil.go:1046 +0x224
     40       /root/tyk/tyk/gateway/testutil.go:1029 +0x19c
     37       /root/tyk/tyk/gateway/testutil.go:1178 +0xe56
     33       /root/tyk/tyk/gateway/server.go:1423 +0x28b
      4       /root/tyk/tyk/gateway/testutil.go:1101 +0xc4
      2       /root/tyk/tyk/gateway/server.go:1421 +0x249
      2       /root/tyk/tyk/gateway/server.go:1420 +0x217
      
root@carbon:~/tyk/tyk/tests/lifecycle# sed -n 1046p /root/tyk/tyk/gateway/testutil.go
	gw := s.newGateway(genConf)
root@carbon:~/tyk/tyk/tests/lifecycle# sed -n 1029p /root/tyk/tyk/gateway/testutil.go
	t.Gw = t.start(genConf)
root@carbon:~/tyk/tyk/tests/lifecycle# sed -n 1178p /root/tyk/tyk/gateway/testutil.go
	gw.afterConfSetup()
root@carbon:~/tyk/tyk/tests/lifecycle# sed -n 1101p /root/tyk/tyk/gateway/testutil.go
	if err := config.WriteDefault("", &gwConfig); err != nil {
root@carbon:~/tyk/tyk/tests/lifecycle# sed -n 1423p /root/tyk/tyk/gateway/server.go
	regexp.ResetCache(time.Second*time.Duration(conf.RegexpCacheExpire), !conf.DisableRegexpCache)
root@carbon:~/tyk/tyk/tests/lifecycle# sed -n 1421p /root/tyk/tyk/gateway/server.go
	rpc.GlobalRPCCallTimeout = time.Second * time.Duration(conf.SlaveOptions.CallTimeout)
root@carbon:~/tyk/tyk/tests/lifecycle# sed -n 1420p /root/tyk/tyk/gateway/server.go
	rpc.GlobalRPCPingTimeout = time.Second * time.Duration(conf.SlaveOptions.PingTimeout)