Fix duplicate iptables rules

If iptables version is < 1.4.11, try to delete the rule vs. checking if it exists. Fixes #6831.

Docker-DCO-1.1-Signed-off-by: Jessica Frazelle <jfrazelle@users.noreply.github.com> (github: jfrazelle)
Add a little description of the image tarball format.

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@docker.com> (github: SvenDowideit)
Fix logDone message for TestCopySingleFileToExistDir

Signed-off-by: Alexandr Morozov <lk4d4@docker.com>
Add Build prefix to Copy tests

Now we can do "-run TestBuild" to test all build-tests and "-run
TestBuildCopy" for test all copy-tests

Signed-off-by: Alexandr Morozov <lk4d4@docker.com>
Merge pull request #8105 from LK4D4/build_test_little_fix

Little fixes in cli build tests
Initialize execStore while restoring a container from checkpoint.

Docker-DCO-1.1-Signed-off-by: Vishnu Kannan <vishnuk@google.com> (github: vishh)
test for panic on daemon restart

Docker-DCO-1.1-Signed-off-by: Jessica Frazelle <jess@docker.com> (github: jfrazelle)
Merge pull request #8115 from vishh/exec_panic_fix

Initialize execStore while restoring a container from checkpoint.
'an file' -> 'a file' grammar fix

Signed-off-by: Albert Callarisa Roca <albert@acroca.com>
Merge pull request #8111 from acroca/master

Grammar fix
Merge pull request #8061 from SvenDowideit/document-image-tarball-format

Add a little description of the image tarball format.
Merge pull request #6950 from jfrazelle/6831-check-flag-centos6.5

Fix duplicate iptables rules