add "if" conditional to avoid looping with a non-existent attribute

[Trenthani]

To help us process your pull request efficiently, please include:

• Added in a hasattr check for the list_virtual_hardware_section. Current behaviour, when running the function with a VM without any disk's an AttributeError is returned. This changes avoids the error and in turn returns no results.

• Testing:
  code snip

def __init__(self, client, vm):
       self.obj = VM(client=client, resource=vm)
       self.vm_resources = self.obj.get_resource()
       virtual_hardware = \
           self.obj.list_virtual_hardware_section(
               is_cpu=True,
               is_memory=True,
               is_disk=True,
               is_media=True,
               is_networkCards=True
               )

Before the change on a vm with no disk, AttributeError was returned.

After, no excetions were raised and the correct info returned.

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This change is