Change e2e regional address to use full subnet path

[spencerhance]

This is a fix for a bug triggered by this PR: #1867

The subnet needs to be provided as a full resource path.

--- PASS: TestILBStaticIP (2287.03s)
    --- PASS: TestILBStaticIP/ilb-static-ip (2287.03s)
        --- PASS: TestILBStaticIP/ilb-static-ip/Transition-0 (270.95s)
        --- PASS: TestILBStaticIP/ilb-static-ip/Transition-1 (31.01s)
        --- PASS: TestILBStaticIP/ilb-static-ip/Transition-2 (30.99s)

/assign @swetharepakula

[k8s-ci-robot]

Hi @spencerhance. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[swetharepakula]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: spencerhance, swetharepakula

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[swetharepakula]

/ok-to-test