Add ability to handle index acknowledgment with splunk log driver
Add ability to handle index acknowledgment with splunk log driver

Previously there was no way for the splunk log driver to work if index
acknowledgment was set on the HEC, and it would in fact fail silently.
This will now allow users to specify if index acknowledgment is set and
will work with that setting.

Signed-off-by: Devon Estes <1eb0783c1b184071cbc6805ed2f974897a27e972@gmail.com>

moby/moby,Ramzec/docker,yongtang/docker,nawawi/docker,ibuildthecloud/docker,konstruktoid/docker-upstream,jimjag/docker,ibuildthecloud/docker,flavio/docker,Ramzec/docker,jthelin/docker,djs55/docker,konstruktoid/docker-1,cpuguy83/docker,docker/docker,jimjag/docker,gnailuy/docker,mahak/docker,nalind/docker,jvanz/docker,yongtang/docker,nawawi/docker,yosifkit/docker,konstruktoid/docker-1,nawawi/docker,cpuguy83/docker,bearstech/moby,jimjag/docker,Mokolea/docker,dims/docker,bearstech/moby,thaJeztah/docker,paralin/docker,jimjag/docker,paralin/docker,moul/docker,thaJeztah/docker,vdemeester/docker,nawawi/docker,nalind/docker,moby/moby,Ramzec/docker,kojiromike/docker,konstruktoid/docker-1,estesp/docker,justincormack/docker,konstruktoid/docker-upstream,moby/moby,bearstech/moby,estesp/docker,AkihiroSuda/docker,moby/moby,docker/docker,gnailuy/docker,yosifkit/docker,AkihiroSuda/docker,jvanz/docker,Mokolea/docker,yosifkit/docker,trebonian/docker,gnailuy/docker,dims/docker,vdemeester/docker,paralin/docker,djs55/docker,flavio/docker,pradipd/moby,ibuildthecloud/docker,justincormack/docker,Mokolea/docker,flavio/docker,ibuildthecloud/docker,ibuildthecloud/docker,estesp/docker,nalind/docker,moul/docker,AkihiroSuda/docker,docker/docker,paralin/docker,gnailuy/docker,flavio/docker,cpuguy83/docker,dims/docker,jvanz/docker,jameszhan/docker,pradipd/moby,yosifkit/docker,pradipd/moby,kojiromike/docker,konstruktoid/docker-upstream,SvenDowideit/docker,mahak/docker,moul/docker,jthelin/docker,jameszhan/docker,mahak/docker,jameszhan/docker,thaJeztah/docker,konstruktoid/docker-upstream,vdemeester/docker,Mokolea/docker,moul/docker,nalind/docker,yongtang/docker,djs55/docker,SvenDowideit/docker,trebonian/docker,trebonian/docker,cpuguy83/docker,justincormack/docker,bearstech/moby,thaJeztah/docker,SvenDowideit/docker,trebonian/docker,kojiromike/docker,Ramzec/docker,AkihiroSuda/docker,mahak/docker