Fix Share Migration tempest tests

This patch addresses issues commented on
change I64b0a3ee77b27278cc294f72702408a27888e0e9
after it was merged, according to bug below.

Closes-bug: #1494000
Change-Id: I9079ea16e0edc359b380705bebba2a7e98446d5c
diff --git a/manila_tempest_tests/config.py b/manila_tempest_tests/config.py
index daed82e..c794168 100644
--- a/manila_tempest_tests/config.py
+++ b/manila_tempest_tests/config.py
@@ -144,6 +144,9 @@
                 help="Defines whether to run consistency group tests or not. "
                      "Disable this feature if used driver doesn't support "
                      "it."),
+    cfg.BoolOpt("run_migration_tests",
+                default=False,
+                help="Enable or disable migration tests."),
     cfg.StrOpt("image_with_share_tools",
                default="manila-service-image",
                help="Image name for vm booting with nfs/smb clients tool."),
@@ -160,7 +163,4 @@
                default=1200,
                help="Time to wait for share migration before "
                     "timing out (seconds)."),
-    cfg.BoolOpt("migration_enabled",
-                default=True,
-                help="Enable or disable migration tests."),
 ]