network: Fix security groups for CentOS

[yadvr]

On RHEL/CentOS/Fedora the bridge related sysctl rules are enabled
in kernel by default but can only be disabled. Enabling those keys
will fail, causing iptables/ebtables tables to not be created
and fails SG on CentOS. Therefore, SG does not work on CentOS.

This also fixes an integration test case, which assumes first few
tests complete within 3 minutes. In nested env the value may be large,
this increases the value to 20 minutes.

Types of changes

• Breaking change (fix or feature that would cause existing functionality to change)
• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Enhancement (improves an existing feature and functionality)
• Cleanup (Code refactoring and cleanup, that may add test cases)

GitHub Issue/PRs

Screenshots (if appropriate):

How Has This Been Tested?

Checklist:

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
  Testing
• I have added tests to cover my changes.
• All relevant new and existing integration tests have passed.
• A full integration testsuite with all test that can run on my environment has passed.

[yadvr]

I've updated docs here:
apache/cloudstack-docs-admin@ea1edc3

[yadvr]

@blueorangutan package

[blueorangutan]

@rhtyd a Jenkins job has been kicked to build packages. I'll keep you posted as I make progress.

[blueorangutan]

Packaging result: ✔centos6 ✔centos7 ✔debian. JID-1966

[yadvr]

@blueorangutan test

[blueorangutan]

@rhtyd a Trillian-Jenkins test job (centos7 mgmt + kvm-centos7) has been kicked to run smoke tests

[wido]

LGTM!

However, still, I think that a admin should set these values manually instead of us changing kernel parameters

[yadvr]

Thanks, agree @wido.

[yadvr]

I'll merge this based on travis results, manual testing (trillian tests don't do sg+centos) and code review.

[blueorangutan]

Trillian test result (tid-2533)
Environment: kvm-centos7 (x2), Advanced Networking with Mgmt server 7
Total time taken: 106241 seconds
Marvin logs: https://github.com/blueorangutan/acs-prs/releases/download/trillian/pr2590-t2533-kvm-centos7.zip
Intermitten failure detected: /marvin/tests/smoke/test_network.py
Intermitten failure detected: /marvin/tests/smoke/test_privategw_acl.py
Smoke tests completed. 66 look OK, 1 have error(s)
Only failed tests results shown below:

Test	Result	Time (s)	Test File
test_03_vpc_privategw_restart_vpc_cleanup	Failure	210.03	test_privategw_acl.py