server: Fix NPE while update displayvm on vm with dynamic service offering

[ustcweizhou]

Description

Steps to reproduce the issue
(1) create a custom service offering
(2) create a vm with the offering
(3) update vm with displayvm=false, returns an error

(local) > update virtualmachine id=f33fd06a-7643-40d1-833f-272845d9ba09 displayvm=false
Error 530: {"updatevirtualmachineresponse":{"uuidList":[],"errorcode":530,"cserrorcode":9999}}

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?

[DaanHoogland]

explicit service offering call instead of generic dao call - lgtm

[andrijapanicsb]

failed to build, wiped the env...

[blueorangutan]

Trillian test result (tid-696)
Environment: kvm-centos7 (x2), Advanced Networking with Mgmt server 7
Total time taken: 35583 seconds
Marvin logs: https://github.com/blueorangutan/acs-prs/releases/download/trillian/pr3758-t696-kvm-centos7.zip
Intermittent failure detected: /marvin/tests/smoke/test_vpc_redundant.py
Smoke tests completed. 76 look OK, 1 have error(s)
Only failed tests results shown below:

Test	Result	Time (s)	Test File
test_05_rvpc_multi_tiers	Failure	416.77	test_vpc_redundant.py
test_05_rvpc_multi_tiers	Error	442.66	test_vpc_redundant.py

[DaanHoogland]

errors seem unrelated, trying insanity
@blueorangutan test

[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-804)
Environment: kvm-centos7 (x2), Advanced Networking with Mgmt server 7
Total time taken: 39094 seconds
Marvin logs: https://github.com/blueorangutan/acs-prs/releases/download/trillian/pr3758-t804-kvm-centos7.zip
Intermittent failure detected: /marvin/tests/smoke/test_vpc_redundant.py
Smoke tests completed. 76 look OK, 1 have error(s)
Only failed tests results shown below:

Test	Result	Time (s)	Test File
test_04_rvpc_network_garbage_collector_nics	Failure	337.54	test_vpc_redundant.py

[DaanHoogland]

regression results spurious, @borisstoyanov @andrijapanicsb