4g-iperf3-bidir: modified the test to parameterize the number of ue in the test.
Parameterize the iperf3 bidirectional test for the 4g test suite to execute a
given number of UEs. By default, the number of ue is 1.
Change-Id:
I34fb436d581eda12388819b5dee9a3bafd419a7f