Adding test case for symlink causes infinit loop, reproduces: dotcloud#5370

normally symlinks are created as either
ln -s /path/existing /path/new-name
or
cd /path && ln -s ./existing new-name

but one can create it this way
cd /path && ln -s existing new-name

this drives FollowSymlinkInScope into infinite loop

Docker-DCO-1.1-Signed-off-by: Lajos Papp <lajos.papp@sequenceiq.com> (github: lalyos)
Defend against infinite loop when following symlinks

ideally it should never reach it, but there was already multiple issues with infinite loop
at following symlinks. this fixes hanging unit tests

Docker-DCO-1.1-Signed-off-by: Lajos Papp <lajos.papp@sequenceiq.com> (github: lalyos)
Fixes 5370 infinite/maxLoopCount loop for relative symlinks

use path.IsAbs() instead of checking if first char is '/'

Docker-DCO-1.1-Signed-off-by: Lajos Papp <lajos.papp@sequenceiq.com> (github: lalyos)
Change libcontainer to drop all capabilities by default. Only keeps
those that were specified in the config. This commit also explicitly
adds a set of capabilities that we were silently not dropping and were
assumed by the tests.

Docker-DCO-1.1-Signed-off-by: Victor Marmol <vmarmol@google.com> (github: vmarmol)
devicemapper: Remove non-general tests

Now that we have the generic graphtest tests that actually tests
the driver we can remove the old mock-using tests. Almost all of
these tests were disabled anyway, and the four remaining ones
didn't really test much while at the same time being really
fragile and making the rest of the code more complex due to
the mocking setup.

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
Typo in execdrivers.go five => give

Docker-DCO-1.1-Signed-off-by: Timothy Hobbs <timothyhobbs@seznam.cz> (github: timthelion)
devmapper: Remove sys.go mocking framework

This is no longer needed, as the tests are gone.

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
run: pull only latest when no tag specified

This makes Docker pull only the image tagged as latest when no tag has
been specified. This makes Docker pull only the image it'll run.

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
Merge pull request #5838 from timthelion/patch-1

Typo in execdrivers.go five => give
server/buildfile: correct daemon.Create comments

s/and start it//

Docker-DCO-1.1-Signed-off-by: Johan Euphrosine <proppy@google.com> (github: proppy)
Merge pull request #5837 from proppy/patch-2

server/buildfile: correct daemon.Create comments
Merge pull request #5842 from alexlarsson/dm-cleanup-tests

 devicemapper: Remove non-general tests
Merge pull request #5841 from unclejack/run_pull_latest

run: pull only latest when no tag specified
Merge pull request #5396 from lalyos/5370-infinite-loop-caused-by-symlink

5370 infinite loop caused by symlink
Merge pull request #5810 from vmarmol/drop-caps

Change libcontainer to drop all capabilities by default.
fix panic when passing empty environment

Docker-DCO-1.1-Signed-off-by: Sridhar Ratnakumar <github@srid.name> (github: srid)
Merge pull request #5833 from ActiveState/fix_nsinit_env_panic

fix panic when passing empty environment