Trivial: Revise the parameter name of event_get2
Trivial: Revise the parameter name of event_get2

This patch revises the name of parameter context in event_get2,
to keep consist with the parameter description.

Change-Id: I245dc5ec6e796825840929f4812da07566f3ab1a

openstack/senlin,openstack/senlin,stackforge/senlin,stackforge/senlin,openstack/senlin