avocado/utils/lv_utils.py: keep thin_lv_create() for compatibility sake

And issue a deprecation warning.  It will then be removed in a couple
of Avocado releases.

Reference: https://trello.com/c/7TBqcAkR/1447-thinlvcreate-deprecate-the-utility-functionSigned-off-by: NCleber Rosa <crosa@redhat.com>

avocado/utils/lv_utils.py

@@ -391,6 +391,27 @@ def lv_create(vg_name, lv_name, lv_size, force_flag=True,
     LOGGER.debug("Created thin volume:%s", lv_name)
 
 
+def thin_lv_create(vg_name, thinpool_name="lvthinpool", thinpool_size="1.5G",
+                   thinlv_name="lvthin", thinlv_size="1G"):
+    """
+    Create a thin volume from given volume group.
+
+    Note: this is a deprecated API and will be removed soon.
+
+    :param vg_name: An exist volume group
+    :param thinpool_name: The name of thin pool
+    :param thinpool_size: The size of thin pool to be created
+    :param thinlv_name: The name of thin volume
+    :param thinlv_size: The size of thin volume
+    """
+    LOGGER.warn("thin_lv_create() is a deprecated API and will be removed "
+                "soon.  Please resort to using lv_create() which is now "
+                "capable of creathing thin logical volumes")
+    lv_create(vg_name=vg_name, lv_name=thinlv_name, lv_size=thinlv_size,
+              pool_name=thinpool_name, pool_size=thinpool_size)
+    return (thinpool_name, thinlv_name)
+
+
 def lv_list(vg_name=None):
     """
     List all info about available logical volumes.