Migrate to pbr.

Fixes bug 1179007

Change-Id: Iceb63c223faab49be01baa36c035f703ddf59fc0
Migrate to flake8.

Fixes bug 1172444.

Change-Id: Icd51f5d925d84dcec7df7c83ca43cd87bc1b090f
Only add logging handlers if there currently aren't any

This corrects an odd problem where Horizon would stand up multiple
client objects, which would cause duplicate/triplicate/dozens of
repeated log lines in its log files, due to multiple identical
handlers being added to the logging object

Fixes Bug 1182678

Change-Id: I020b3999c9008b996286ccb74a7801c96c43e71c
Default signing_dir to secure temp dir (bug 1181157)

Change-Id: I1a29f50b07a60de3d0519bf40074dbea92fa8656
Merge "Migrate to pbr."
Merge "Migrate to flake8."
Merge "Only add logging handlers if there currently aren't any"
Merge "Default signing_dir to secure temp dir (bug 1181157)"