Make TenantID not required for lbaas member creation (#72)

diff --git a/openstack/networking/v2/extensions/lbaas/members/requests.go b/openstack/networking/v2/extensions/lbaas/members/requests.go
index f74eb82..7e7b768 100644
--- a/openstack/networking/v2/extensions/lbaas/members/requests.go
+++ b/openstack/networking/v2/extensions/lbaas/members/requests.go
@@ -56,7 +56,7 @@
 	PoolID string `json:"pool_id" required:"true"`
 	// Only required if the caller has an admin role and wants to create a pool
 	// for another tenant.
-	TenantID string `json:"tenant_id,omitempty" required:"true"`
+	TenantID string `json:"tenant_id,omitempty"`
 }
 
 func (opts CreateOpts) ToLBMemberCreateMap() (map[string]interface{}, error) {