Do it only when the governor tells to. When `_G.vshard == nil`, it's
more alike `traft::node::global()` which reurns either `Ok` or
`Err(Uninitialized)`.

It produces better error messages.

Before this commit:

```
tarantool> vshard.router.call()
---
- error: '[string "local log = require(''log'')..."]:575: attempt to
    compare number with nil'
...
```

With this commit:

```
- error: 'vshard/router/init.lua:575: attempt to compare number with
    nil'
```

add roadmap-en

Example:

```console
tarantool> picolib.whoami()
---
- raft_id: 1
  cluster_id: demo
  instance_id: i1
...

tarantool> picolib.peer_info("i1")
---
- raft_id: 1
  instance_id: i1
  instance_uuid: 68d4a766-4144-3248-aeb4-e212356716e4
  replicaset_uuid: e0df68c5-e7f9-395f-86b3-30ad9e1b7b07
  replicaset_id: r1
  advertise_address: localhost:3301
  target_grade: Online
  current_grade: Online
...
```

Alexey Protsenko authored 2 years ago and Yaroslav Dynnikov committed 2 years ago

1. Signed rpm packages used to be overridden by unsigned
   ones due to the artifacts clash. This bug is fixed by
   specifying explicit stage dependencies.
2. Add stage for testing installed packages.