CI: adding profiling option to iperf:

 -- balanced (current version): all UE shares the same BW
 -- single-ue : one UE will use the whole requested BW
 -- unbalanced : all but one UE will use a residual 2% of the requested BW
                 the rest of requested BW will be used by one UE

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>