VMware: use default values in get_info() when properties are missing

The properties that we retrieve from VirtualMachineConfigSummary are
optional ('summary.config.numCpu', 'summary.config.memorySizeMB') and
if they are missing we should return default values from get_info()

This patch also improves the unit test for get_info(). It removes the
test in test_driver_api.py (test_get_info() and test_spawn() are the
same) and adds a new test in test_vmops.py

Conflicts:

	nova/tests/virt/vmwareapi/test_driver_api.py
	nova/tests/virt/vmwareapi/test_vmops.py

Closes-Bug: 1317912
Change-Id: Ibbb28985d13de371fdac8a119ad820d25acc21be
(cherry picked from commit 2db7528ca258d7b0c1205ab2f9a76569d9f9a82d)
Merge "VMware: use default values in get_info() when properties are missing" into stable/icehouse