tarsum: TarSum is not the interface

don't export the exsisting TarSum struct and call the interface 'TarSum'
instead.

Signed-off-by: Vincent Batts <vbatts@redhat.com>
Add Test for port allocation bug (port already in use by other programs than docker)

Signed-off-by: Tibor Vass <teabee89@gmail.com>
Fix an issue where already allocated ports would not trigger an error.

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
Fix my own comments from #7927

Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com>
Signed-off-by: David Gebler <davidgebler@gmail.com>

	modified:   userguide/dockerlinks.md
    fixes incorrect environment variable labeling in container linking guide
Ensure container names start with a-zA-Z0-9

Closes #8012.

Docker-DCO-1.1-Signed-off-by: Jessica Frazelle <jess@docker.com> (github: jfrazelle)
Merge pull request #7934 from LK4D4/fix_double_allocation

Fix error propagation from userland-proxy
Fix parsing of proto/port

Signed-off-by: Doug Davis <dug@us.ibm.com>
Merge pull request #8004 from duglin/Issue6447

Fix parsing of proto/port - issue 6447
Merge pull request #8014 from jfrazelle/8012-prevent-container-names-starting-dash

Ensure container names start with a-zA-Z0-9
Merge pull request #7983 from vbatts/vbatts-tarsum_switch_names

tarsum: TarSum should be the interface
Merge pull request #8008 from dwgebler/master

fixes incorrect environment variable labeling in container linking guide
HTTP Status 201 not 200

The http status should be 201 not 200.

Docker-DCO-1.1-Signed-off-by: Erik Kristensen <erik@erikkristensen.com> (github: SvenDowideit)
Merge pull request #8028 from SvenDowideit/ekristen-patch-1

HTTP Status 201 not 200