dbjobsource: extract method handling cancelling jobs
dbjobsource: extract method handling cancelling jobs

Change-Id: I2184654c087f54400fc62e8dfd19b210c0e2c3d9

OSSystems/lava-server,Linaro/lava-server,Linaro/lava-server,Linaro/lava-server,OSSystems/lava-server,Linaro/lava-server,OSSystems/lava-server