Merge: * set BlockingMode: "null_ip" by default; minor improvements

Squashed commit of the following:

commit 653544b98dc4d1b9a74e1509d0e6104b71bcdcb3
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Wed Dec 11 17:34:41 2019 +0300

    * DNS reconfigure: protect against delayed socket fd close

commit 9e650f37dee7f771bf1d9d714c35f0a81788aa16
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Wed Dec 11 15:28:33 2019 +0300

    - fix race on startup

commit 878fdb8fc4ebbc6fab683a65f5e4298e64c2073e
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Wed Dec 11 15:11:21 2019 +0300

    * travis: don't run tests

commit 1c4ab60684ee22d55e6d2a3350c0f24d9844255c
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Wed Dec 11 14:56:28 2019 +0300

    * travis: 'release.sh' and then run tests

commit e1f644b8d9a1f3b46990cdfb1b75fd81b3a49d33
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Wed Dec 11 14:52:59 2019 +0300

    * set BlockingMode: "null_ip" by default

.travis.yml

@@ -42,8 +42,6 @@ matrix:
       script:
         - node -v
         - npm -v
-        # Run tests just in case
-        - go test -race -v -bench=. ./...
         # Prepare releases
         - ./release.sh
         - ls -l dist