server: acquire IPv4 address when add secondary IP to nic if IP is not specified

[ustcweizhou]

Description

After commit fbf4884, admin need to specify an ipv4 or ipv6 addresses when add IP to nic which breaks backward compatibity. If IP is not specified, a IPv4 address should be returned.

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?

When I add an IP to a nic and do not specify an IP,

Before this PR, it gives an error "Allocating ip to guest nic 111 failed"
After this PR, it succeeds.

[ustcweizhou]

@wido@GabrielBrascher @rhtyd
can you please review and test it ?

[GabrielBrascher]

Code LGTM, thanks @ustcweizhou.

[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-344

[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-503)
Environment: kvm-centos7 (x2), Advanced Networking with Mgmt server 7
Total time taken: 27830 seconds
Marvin logs: https://github.com/blueorangutan/acs-prs/releases/download/trillian/pr3635-t503-kvm-centos7.zip
Smoke tests completed. 77 look OK, 0 have error(s)
Only failed tests results shown below:

Test	Result	Time (s)	Test File