Make remote API unit tests easier to read and write

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
Update dns and volumes-from docs
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Check for apparmor enabled on host to populate profile
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Merge pull request #5104 from crosbymichael/update-dns-vf-docs

Update dns and volumes-from docs
Fix spurious mtab symlink error when /etc doesn't exist yet

symlink /proc/mounts /var/lib/docker/btrfs/subvolumes/1763d6602b8b871f0a79754f1cb0a31b3928bb95de5232b1b8c15c60fa1017f6-init/etc/mtab: no such file or directory

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Merge pull request #5102 from shykes/api-cleanup-tests

Make remote API unit tests easier to read and write
Merge pull request #5127 from crosbymichael/update-apparmor

Check for apparmor enabled on host to populate profile
Merge pull request #5134 from tianon/fix-mtab-symlink-error

Fix spurious mtab symlink error when /etc doesn't exist yet
Change owner only on copied content

Fixes #5110
Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)