pyocf: add FLUSH flag

Flush I/O must be recognized by the bottom adapter by inspecting
adapter specific flags

Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>

tests/functional/pyocf/types/volume.py

@@ -22,6 +22,7 @@ from ctypes import (
 )
 from hashlib import md5
 import weakref
+from enum import IntEnum
 
 from .io import Io, IoOps, IoDir
 from .queue import Queue
@@ -32,6 +33,10 @@ from .data import Data
 from .queue import Queue
 
 
+class IoFlags(IntEnum):
+    FLUSH = 1
+
+
 class VolumeCaps(Structure):
     _fields_ = [("_atomic_writes", c_uint32, 1)]
 
@@ -350,6 +355,11 @@ class RamVolume(Volume):
             discard.contents._end(discard, -OcfErrorCode.OCF_ERR_NOT_SUPP)
 
     def do_submit_io(self, io):
+        flags = int(io.contents._flags)
+        if flags & IoFlags.FLUSH:
+            self.do_submit_flush(io)
+            return
+
         try:
             io_priv = cast(OcfLib.getInstance().ocf_io_get_priv(io), POINTER(VolumeIoPriv))
             offset = io_priv.contents._offset