cartridge: improve run dir path detection

[psergee]

The command will use tt environment run dir path for searching control sockets.

Manual tests:

$ tt init
   • Found existing config '.cartridge.yml'
   • Environment config is written to 'tt.yaml'

$ tt start
   • Starting an instance [myapp:s2-replica]...
   • Starting an instance [myapp:stateboard]...
   • Starting an instance [myapp:router]...
   • Starting an instance [myapp:s1-master]...
   • Starting an instance [myapp:s1-replica]...
   • Starting an instance [myapp:s2-master]...

$ tt cartridge replicasets setup --bootstrap-vshard
   • Set up replicasets described in /home/user/myapp/replicasets.yml
   • router... CREATED
   • s-1... CREATED  
   • s-2... CREATED  
   • Replicasets are set up successfully
   • Bootstrap vshard task completed successfully, check the cluster status

$ tt cartridge replicasets list
   • Current replica sets:
• router
  Role: failover-coordinator | vshard-router | app.roles.custom
    ★ router localhost:3301
• s-1                    default | 1
  Role: vshard-storage
    ★ s1-master localhost:3302
    • s1-replica localhost:3303
• s-2                    default | 1
  Role: vshard-storage
    ★ s2-master localhost:3304
    • s2-replica localhost:3305

$ tt cartridge admin -l --name myapp
   • Available admin functions:

probe  Probe instance

Closes #407