[18.03] Possible race on ingress programming

[thaJeztah]

backport of #2178 for the bump18.03 branch

git checkout -b 18.03-backport-race-ingress upstream/bump_18.03
git cherry-pick -s -S -x 7bb62d0172f8e676388d4d78e510c4d9fd4c1d06
git push -u origin

no conflicts

Make sure that iptables operations on ingress
are serialized.
Before 2 racing routines trying to create the ingress chain
were allowed and one was failing reporting the chain as
already existing.
The lock guarantees that this condition does not happen anymore

Signed-off-by: Flavio Crisciani flavio.crisciani@docker.com
(cherry picked from commit 7bb62d0)
Signed-off-by: Sebastiaan van Stijn github@gone.nl

[fcrisciani]

LGTM

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (bump_18.03@3931ba4). Click here to learn what that means.
The diff coverage is 0%.

@@             Coverage Diff              @@
##             bump_18.03   #2181   +/-   ##
============================================
  Coverage              ?   40.6%           
============================================
  Files                 ?     139           
  Lines                 ?   22484           
  Branches              ?       0           
============================================
  Hits                  ?    9129           
  Misses                ?   12024           
  Partials              ?    1331

Impacted Files	Coverage Δ
service_linux.go	3.2% <0%> (ø)

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