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
Decouple resources and preconditions in secgroup scenario

Handle secondary tenant checks based on CONF file only instead of using clients

Skip only cross-tenant test instead of whole class if secondary tenant is not
available

Change-Id: I9863ff840b9c5b18fa46826aab3fc107454dcc24
Remove a redundant KeyPairsV3ClientJSON

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

Change-Id: Ia19e8db43d601c7ca919820c62da699e660e0623
Fixes grammatical errors in HACKING.rst

There are a few lines in HACKING.rst that were incorrect
grammatically. This fix changes those.

Change-Id: I8173dae3cf3a3e78a504b4edd4a7c1ff5b7fb9a4
Closes-Bug: #1389603
Merge "Remove a redundant KeyPairsV3ClientJSON"
Merge "Use "ip" instead of "ifconfig" to get MAC address"
Stop resource leakage for negative tests

get_client_manager should only create a new isolated_creds class if
there isn't already a isolated_creads instance bound to the test.

Change-Id: I44fd05d3c1dc713ec7bd176af689b008fbb5d7eb
Fixes-bug: #1371706
Merge "Stop resource leakage for negative tests"
Merge "Fixes grammatical errors in HACKING.rst"
Merge "Decouple resources and preconditions in secgroup scenario"