Migrate TestGetImagesHistory into unit and CLI test

Docker-DCO-1.1-Signed-off-by: Adrien Folie <folie.adrien@gmail.com> (github: folieadrien)
Add missing test for full coverage

Docker-DCO-1.1-Signed-off-by: Adrien Folie <folie.adrien@gmail.com> (github: folieadrien)
integration cli: add imageExists to docker utils

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
make TestRemoveContainerRunning handle signals

This lowers the test execution time by about 5 seconds.

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
Add NOFILE and NPROC ulimit settings to the OpenRC init script

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Add NOFILE and NPROC ulimit settings to the SysV init script

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
integcli: add & use pullImageIfNotExist for pulls

This speeds up the tag cli integration tests by about 20 seconds.

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
Merge pull request #6814 from tianon/more-init-ulimit

Add NOFILE and NPROC ulimit settings to OpenRC and SysVinit
Merge pull request #6763 from folieadrien/master

Migrate TestGetImagesHistory into unit and CLI test
Merge pull request #6780 from unclejack/tweak_cli_integration_tests

Tweak cli integration tests