Improving the time to wait for assigning IP address

Framework always spends 600msec for getting IP address.
DhcpStateMachine.runDhcp calls NetworkUtils.stopDhcp.
After that, it calls NetworkUtils.runDhcp.
In this case, wait_for_property of dhcp_utils.c calls three times.
At least three times, usleep is called.
So move usleep statement after property_get statement.

Change-Id: I77ffb9a5a64875b47bb528b494bb60b68c1acb5a