Fix sipp problems on running.

After -s option doesn't have whitespace, when running sipp need
whitespace for interpret remote host.

Invalid
  sudo sipp -i 192.168.1.114 -p 8836 -sf /Users/eloycotopereiro/dev/sipp/sippcup/my_test_scenario.xml -l 10 -m 20 -r 5 -s 1192.168.1.120

Valid
  sudo sipp -i 192.168.1.114 -p 8836 -sf /Users/eloycotopereiro/dev/sipp/sippcup/my_test_scenario.xml -l 10 -m 20 -r 5 -s 1 192.168.1.120


Cheers