globalDeploymentID was being read while it was being set.
Fixes race:
```
WARNING: DATA RACE
Write at 0x0000079605a0 by main goroutine:
github.com/minio/minio/cmd.connectLoadInitFormats()
github.com/minio/minio/cmd/prepare-storage.go:269 +0x14f0
github.com/minio/minio/cmd.waitForFormatErasure()
github.com/minio/minio/cmd/prepare-storage.go:294 +0x21d
...
Previous read at 0x0000079605a0 by goroutine 105:
github.com/minio/minio/cmd.newContext()
github.com/minio/minio/cmd/utils.go:817 +0x31e
github.com/minio/minio/cmd.adminMiddleware.func1()
github.com/minio/minio/cmd/admin-router.go:110 +0x96
net/http.HandlerFunc.ServeHTTP()
net/http/server.go:2136 +0x47
github.com/minio/minio/cmd.setBucketForwardingMiddleware.func1()
github.com/minio/minio/cmd/generic-handlers.go:460 +0xb1a
net/http.HandlerFunc.ServeHTTP()
net/http/server.go:2136 +0x47
...
```
