Declare multiattach is True in Dell Eqlx driver

An Eqlx volume can be attached to multi instances, however,
this feature is not declared in eqlx driver. As a result,
if a user create a multi-attached volume using eqlx as
backend, they will be failed.

In this commit, we declared multiattach is True in eqlx
driver.

Change-Id: Ia8e94e739c2573f1f26d8cb2713a6b851adf9428
Closes-Bug: #1519570

cinder/tests/unit/test_eqlx.py

@@ -297,6 +297,7 @@ class DellEQLSanISCSIDriverTestCase(test.TestCase):
             self.assertEqual(not thin_enabled,
                              stats['thick_provisioning_support'])
             self.assertEqual('Dell', stats['vendor_name'])
+            self.assertTrue(stats['multiattach'])
 
     def test_get_space_in_gb(self):
         self.assertEqual(123.0, self.driver._get_space_in_gb('123.0GB'))

cinder/volume/drivers/eqlx.py

@@ -326,6 +326,7 @@ class DellEQLSanISCSIDriver(san.SanISCSIDriver):
 
         data['total_capacity_gb'] = 0
         data['free_capacity_gb'] = 0
+        data['multiattach'] = True
 
         provisioned_capacity = 0