Remove the deprecated argument tenant from RequestContext
Remove the deprecated argument tenant from RequestContext

Change I2fded6f3476df1fb8c4e042ef28ed8ccb7ab0737 in oslo_context removed
the long deprecated tenant argument. Change it in magnum.

Change-Id: Ie30c41b2c5c41a38c25c60f089bebb048328989a

openstack/magnum,openstack/magnum,ArchiFleKs/magnum,ArchiFleKs/magnum