Use "ip" instead of "ifconfig" to get MAC address

"ifconfig" get different formats of output under different systems,
like CentOS and Fedora, but "ip" can provide uniform format, so we
use "ip" instead of "ifconfig" to get MAC address.

Change-Id: If7559ea96c96ed2f33ddb00737ee0f53f7de4990
Closes-Bug: 1381416
Skip some tests when cinder is not enabled

test_delete_server_while_in_attached_volume:
    Skip when cinder is not enabled.
ServerRescueTestJSON:
    No test access the volume resource_setup creates, so stop creating one.
ServerRescueNegativeTestJSON:
    Move volume creation into tests that use it and skip them when cinder
    is not enabled.

Change-Id: I8587c3e5ff3dbf5f23d09a5fd49b2c55c2ef7657
Remove a redundant KeyPairsV3ClientJSON

There are duplicated KeyPairsV3ClientJSON settings in __init__()
of Manager class. This patch removes it.

Change-Id: Ia19e8db43d601c7ca919820c62da699e660e0623
Merge "Skip some tests when cinder is not enabled"
Merge "Remove a redundant KeyPairsV3ClientJSON"
Merge "Use "ip" instead of "ifconfig" to get MAC address"
Merge branch 'master' of https://github.com/openstack/tempest