Fix dhcp wait

[vbauzys]

Fix: vmware/terraform-provider-vcd#666

verified that current test isn't broken:

START: vm_dhcp_test.go:26: TestVCD.Test_VMGetDhcpAddress
# Time out waiting for DHCP IPs on powered off VMs: OK
# Get IPs for NICs 0 and 1: OK:(NICs 0 and 1): 32.32.32.22, 32.32.32.21
# Get active lease for NICs with MAC 0: Ok. (Got active lease for MAC 0: 32.32.32.22)
# Check number of leases on Edge Gateway: OK: (4 leases found)
# Get IP for single NIC 0: OK: Got IP for NICs 0: 32.32.32.22
# Get IPs for NICs 0 and 1 (only using guest tools): OK: IPs for NICs 0 and 1 (via guest tools): 32.32.32.22, 32.32.32.21
PASS: vm_dhcp_test.go:26: TestVCD.Test_VMGetDhcpAddress	300.330s

START: api_vcd_test.go:1554: TestVCD.TearDownSuite
# 1 of 3 - removeLeftoverEntries: [INFO] Attempting cleanup of vapp 'TestSetUpSuite' instantiated by createTestVapp
removeLeftoverEntries: [INFO] Removed vapp 'TestSetUpSuite' created by createTestVapp
# 2 of 3 - removeLeftoverEntries: [INFO] Attempting cleanup of vapp 'GetDhcpAddress' instantiated by createTestVapp
removeLeftoverEntries: [INFO] No action for vapp 'GetDhcpAddress'
# 3 of 3 - removeLeftoverEntries: [INFO] Attempting cleanup of network 'TestCreateOrgVdcNetworkDhcp' instantiated by TestCreateOrgVdcNetworkDhcp
removeLeftoverEntries: [INFO] Removed network 'TestCreateOrgVdcNetworkDhcp' created by TestCreateOrgVdcNetworkDhcp
PASS: api_vcd_test.go:1554: TestVCD.TearDownSuite	59.053s

OK: 1 passed
PASS

new test isn't added as it will be big and complicated and we have limited NSXV support.

[lvirbalas]

Nice :)

[mikeletux]

Great, thanks!