[minor] add support for in-flight action cacheing
[minor] add support for in-flight action cacheing

This is intended to cover a case where an action is generated by the
runner, but the runner is restarted before the results are available.
Actions are cached on disk while in-flight and can now persist through
restarts of the service.

sunnygkp10/mig,gdestuynder/mig,pap/mig,sunnygkp10/mig,pap/mig,jboyer2012/mig,vladimirdiaconescu/mig,gdestuynder/mig,mozilla/mig,therealkbhat/mig,pap/mig,mozilla/mig,jboyer2012/mig,gdestuynder/mig,vladimirdiaconescu/mig,ameihm0912/mig,mozilla/mig,therealkbhat/mig,mvanotti/mig,pap/mig,mozilla/mig,mvanotti/mig,ameihm0912/mig,yvesago/mig,mvanotti/mig,rezen/mig,vladimirdiaconescu/mig,therealkbhat/mig,therealkbhat/mig,sunnygkp10/mig,rezen/mig,mozilla/mig,jboyer2012/mig,mvanotti/mig,yvesago/mig,ameihm0912/mig,rezen/mig,sunnygkp10/mig,yvesago/mig,vladimirdiaconescu/mig,gdestuynder/mig,yvesago/mig,rezen/mig,jboyer2012/mig