use docker exec instead of docker cp .

[xuxinkun]

SUMMARY

Use docker exec instead of docker cp in case some versions of docker not support cp.

ISSUE TYPE

• Bugfix Pull Request

COMPONENT NAME

docker connection plugin

ANSIBLE VERSION

devel

ADDITIONAL INFORMATION

In some old version, docker did not support cp command. So, I use exec -i dd instead of cp to support fetch file.

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[bcoca]

I would implement this as a fallback if the cp fails instead of the main way to copy files.

[xuxinkun]

@bcoca OK, I modify my code. If cp fails, try to use exec instead.