[PATCH v2] untar: do not exit with error when created directory already exists.

[Pavel Pisa]

Hello Chris and Gedare,

I have updated fix of untar problem which has been
introduced during 4.11 development cycle.
The file in a way of created directory is unlinked
per Chris request.

Code is duplicated over all untar implementations
but I would keep this minimal patch for now.
It could be applied to master and 4.11.

Then untar code unification should be developed
for master. Introduction of option to pass source
source through unzip would worth to add as well.

Best wishes,

               Pavel