host.py: method to get all the mac addresses

[abdhaleegit]

Gets you a list of all hardware addresses for the
given host (local and remote)

[mr-avocado]

Dear contributor,
Avocado is currently under sprint #103, which is due to release an LTS (Long Term Stability) release.
Please avoid merging changes that do not fall into these categories:

• Bug fixes
• Usability Improvements
• Documentation updates

As for the Avocado utility modules (“avocado.utils”) it is OK to introduce new functionality,
but changes to the existing APIs (including interface and behavior) should be avoided.
These kind of changes should wait until sprint #104.

[abdhaleegit]

Works fine for both local and remote host, this will be used in test to validate if given mac exists in the list

        local = LocalHost()
        print(local.get_all_hwaddr())

        self.remotehost = RemoteHost(self.peer, self.peer_user,
                                                          password=self.peer_password)
        print(self.remotehost.get_all_hwaddr())

[Naresh-ibm]

LGTM
just take care of build failures

[richtja]

LGTM