Fix RESERVATIONS display in fleets table

[r4victor]

Fixes a bug introduced in #1977

The RESERVATION column in fleets table wasn't properly filled:

Found fleet my-ssh-fleet. Configuration changes detected.
Re-create the fleet? [y/n]: y
 FLEET         RESERV…  INSTAN…  BACKEND  RESOUR…  PRICE   STATUS   CREAT…  ERROR   
 my-ssh-fleet           0        ssh      2xCPU,   $0.0    termin…  16:37   Provis… 
                                 (remot…  0GB,                              timeout 
                                          100.0GB                           expired 
                                          (disk)                                    
               1        ssh      2xCPU,   $0.0     termi…  16:37    Provi…          
                        (remot…  0GB,                               timeo…          
                                 100.0GB                            expir…          
                                 (disk)