api: postImagesCreate(): rename ambiguous err variable
api: postImagesCreate(): rename ambiguous err variable

This error is meant to be used in the output stream, and some comments
were added to prevent accidentally using local variables.

Renaming the variable instead to make it less ambiguous.

Signed-off-by: Sebastiaan van Stijn <64b2b6d12bfe4baae7dad3d018f8cbf6b0e7a044@gone.nl>

thaJeztah/docker,yosifkit/docker,konstruktoid/docker-upstream,mahak/docker,bearstech/moby,cpuguy83/docker,jimjag/docker,gnailuy/docker,nawawi/docker,nawawi/docker,jimjag/docker,gnailuy/docker,Ramzec/docker,mahak/docker,flavio/docker,moby/moby,nalind/docker,yosifkit/docker,nawawi/docker,cpuguy83/docker,Mokolea/docker,nalind/docker,Mokolea/docker,mahak/docker,vdemeester/docker,moby/moby,thaJeztah/docker,mahak/docker,flavio/docker,nalind/docker,moul/docker,moby/moby,trebonian/docker,flavio/docker,trebonian/docker,trebonian/docker,nalind/docker,yosifkit/docker,bearstech/moby,cpuguy83/docker,konstruktoid/docker-upstream,yosifkit/docker,Ramzec/docker,trebonian/docker,vdemeester/docker,bearstech/moby,flavio/docker,jimjag/docker,moby/moby,thaJeztah/docker,Ramzec/docker,vdemeester/docker,konstruktoid/docker-upstream,Mokolea/docker,bearstech/moby,Mokolea/docker,gnailuy/docker,moul/docker,nawawi/docker,moul/docker,thaJeztah/docker,moul/docker,konstruktoid/docker-upstream,cpuguy83/docker,Ramzec/docker,gnailuy/docker,jimjag/docker