bisect-kit: Add option to lease specific dut

BUG=b:154729940
TEST=./cros_helper.py allocate_dut --dut_name chromeos1-row1-rack11-host6 --session test
TEST=./cros_helper.py release_dut --session test chromeos1-row1-rack11-host6.cros

Change-Id: I43209a838215e62bc4f2a6a96860cc8607f07c90
2 files changed