Add oslo.context dependency

This is used in os_brick/executor.py.

This mirrors change I98c332841 from
stable/victoria.

Change-Id: I28d22dacc595bc034a0eacb3d1a72848644ad9d8

requirements.txt

@@ -6,6 +6,7 @@ pbr!=2.1.0,>=2.0.0 # Apache-2.0
 Babel!=2.4.0,>=2.3.4 # BSD
 eventlet!=0.18.3,!=0.20.1,>=0.18.2 # MIT
 oslo.concurrency>=3.26.0 # Apache-2.0
+oslo.context>=2.19.2 # Apache-2.0
 oslo.log>=3.36.0 # Apache-2.0
 oslo.i18n>=3.15.3 # Apache-2.0
 oslo.privsep>=1.23.0 # Apache-2.0