Fix IndexOutOfBoundsException when creating basic network

[slavkap]

Description

For Basic network isolation methods are not provided, and exception is
thrown when trying to encode the Vlan id. That's why we have to check
before encoding that the list with isolation methods is not empty

Reported issue #4450

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)

Screenshots (if appropriate):

How Has This Been Tested?

on branch 4.13 and master
Setup CloudStack through the old UI with the installation wizard (which creates Basic network).

[sureshanaparti]

Changes LGTM

[weizhouapache]

code lgtm

[DaanHoogland]

@GabrielBrascher i think this concerns your remark on the subject, can you test?
@blueorangutan package

[blueorangutan]

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

[blueorangutan]

Packaging result: ✔centos7 ✖centos8 ✔debian. JID-2374

[DaanHoogland]

@blueorangutan test

[blueorangutan]

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

[blueorangutan]

Trillian test result (tid-3160)
Environment: kvm-centos7 (x2), Advanced Networking with Mgmt server 7
Total time taken: 26425 seconds
Marvin logs: https://github.com/blueorangutan/acs-prs/releases/download/trillian/pr4464-t3160-kvm-centos7.zip
Intermittent failure detected: /marvin/tests/smoke/test_privategw_acl.py
Smoke tests completed. 76 look OK, 1 have error(s)
Only failed tests results shown below:

Test	Result	Time (s)	Test File
test_02_vpc_privategw_static_routes	Failure	169.26	test_privategw_acl.py
test_03_vpc_privategw_restart_vpc_cleanup	Failure	166.09	test_privategw_acl.py
test_04_rvpc_privategw_static_routes	Failure	216.62	test_privategw_acl.py

[DaanHoogland]

taking a leap here as it only adds a guard extra. we'll have to merge forward and test the result.

[GabrielBrascher]

It was merged but I am adding my test feedback anyway :)

Tested and it works +1 👍