Bump os-brick version to 2.6.1

This will get us bug fixes for gate bug:

  https://bugs.launchpad.net/nova/+bug/1732199

and another bug that looks like it could affect the gate:

  https://bugs.launchpad.net/os-brick/+bug/1794829

Closes-Bug: #1732199

Change-Id: I709b4a1438aedcfc95d191462b4ec3f1f8c4355a

lower-constraints.txt

@@ -67,7 +67,7 @@ netifaces==0.10.4
 networkx==1.11
 numpy==1.14.2
 openstacksdk==0.12.0
-os-brick==2.5.0
+os-brick==2.6.1
 os-client-config==1.29.0
 os-service-types==1.2.0
 os-traits==0.4.0

requirements.txt

@@ -54,7 +54,7 @@ rfc3986>=0.3.1 # Apache-2.0
 oslo.middleware>=3.31.0 # Apache-2.0
 psutil>=3.2.2 # BSD
 oslo.versionedobjects>=1.31.2 # Apache-2.0
-os-brick>=2.5.0 # Apache-2.0
+os-brick>=2.6.1 # Apache-2.0
 os-traits>=0.4.0 # Apache-2.0
 os-vif!=1.8.0,>=1.7.0 # Apache-2.0
 os-win>=3.0.0 # Apache-2.0