ibm flashsystem: Fixing hardcoded attribute

In FlashSystem driver, flashsystem_common.py, the attribute
"multiattach" has been hard coded as "True", this attribute value
should be read from the configuration file.
The property name is "flashsystem_multihost_enabled".

This bug will force the customers to run all operations in
multi-attached environment.

Change-Id: Id092c51e565052c5eef2d3381d53f5788a97d9cc
Closes-Bug: #1572743

cinder/tests/unit/test_ibm_flashsystem.py

@@ -1021,6 +1021,7 @@ class FlashSystemDriverTestCase(test.TestCase):
     def test_flashsystem_get_volume_stats(self):
         # case 1: good path
         self._set_flag('reserved_percentage', 25)
+        self._set_flag('flashsystem_multihostmap_enabled', False)
         pool = 'mdiskgrp0'
         backend_name = 'flashsystem_1.2.3.4' + '_' + pool
 
@@ -1030,6 +1031,7 @@ class FlashSystemDriverTestCase(test.TestCase):
         self.assertEqual('IBM', stats['vendor_name'])
         self.assertEqual('FC', stats['storage_protocol'])
         self.assertEqual(backend_name, stats['volume_backend_name'])
+        self.assertEqual(False, stats['multiattach'])
 
         self._reset_flags()
 

cinder/volume/drivers/ibm/flashsystem_common.py

@@ -858,7 +858,7 @@ class FlashSystemDriver(san.SanDriver):
             'free_capacity_gb': 0,
             'reserved_percentage': self.configuration.reserved_percentage,
             'QoS_support': False,
-            'multiattach': True,
+            'multiattach': self.configuration.flashsystem_multihostmap_enabled,
         }
 
         pool = FLASHSYSTEM_VOLPOOL_NAME