LU-8636 build: prevent src download at the same time

LU-8636 build: prevent src download at the same time

If the lbuild kernelsrc/kernelrpm directory is shared
among the builders, we need to keep them from using
it while it's being downloaded

Test-Parameters: trivial

Change-Id: I240996c84ea541f5985b8d6ec73e3c6a56d2d805
Signed-off-by: Minh Diep <minh.diep@intel.com>
Reviewed-on: http://review.whamcloud.com/22939
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>