[director] Fix tracking preparing package compilation stage

Actually the "Preparing package compilation" stage doesn't behave like the rest of stages (it does not print the stage tasks):

```
Preparing deployment
  binding deployment (00:00:00)                                                                     
  binding releases (00:00:01)                                                                       
  binding existing deployment (00:00:00)                                                            
  binding resource pools (00:00:00)                                                                 
  binding stemcells (00:00:00)                                                                      
  binding templates (00:00:00)                                                                      
  binding properties (00:00:00)                                                                     
  binding unallocated VMs (00:00:00)                                                                
  binding instance networks (00:00:00)                                                              
Done                    9/9 00:00:01                                                                

Preparing package compilation

Compiling packages
```

This PR will fix this, so the output will be:

```
Preparing deployment
  binding deployment (00:00:00)                                                                     
  binding releases (00:00:00)                                                                       
  binding existing deployment (00:00:00)                                                            
  binding resource pools (00:00:00)                                                                 
  binding stemcells (00:00:00)                                                                      
  binding templates (00:00:00)                                                                      
  binding properties (00:00:00)                                                                     
  binding unallocated VMs (00:00:00)                                                                
  binding instance networks (00:00:00)                                                              
Done                    9/9 00:00:00                                                                

Preparing package compilation
  finding packages to compile (00:00:07)                                                            
Done                    1/1 00:00:07                                                                

Compiling packages
```