Use guaranteed memory resources when memory overhead is included in tests

[Didainius]

Improved VCD API validation detected a quirk where a configuration was not exactly correct. Quite a few tests fail now (all that spawn VDCs for testing purposes). The fix is to set ResourceGuaranteedMemory when spawning a Flex VDC

Tests that it should fix:

• TestQueryOrgVdcList
• Test_CreateOrgVdcWithFlex
• Test_CreateVdcGroup
• Test_GetCatalogByIdSharedCatalog
• Test_GetCatalogByNamePrefersLocal
• Test_GetCatalogByNameSharedCatalog
• Test_GetCatalogByXSharedCatalogOrgUser
• Test_NsxtApplicationPortProfileProvider
• Test_NsxtApplicationPortProfileTenant
• Test_NsxtDistributedFirewallRules
• Test_NsxtDistributedFirewallRule
• Test_NsxtDistributedFirewallWithDefaultRule
• Test_NsxtEdgeVdcGroup
• Test_NsxtOrgVdcNetworkImportedNsxtLogicalSwitch
• Test_NsxtStaticSecurityGroup
• Test_NsxtVdcGroupOrgNetworks
• Test_NsxtVdcGroupWithOrgAdmin
• Test_SearchOrgVdc