fix(FileSR): preserve image-format during DB update (#140)

This field can be removed during VDI actions like `resize`.
Fixed using `_override_sm_config` to keep the value like for `vhd-parent`

Signed-off-by: Erwan Croze <erwan.croze@vates.tech>

Author: DatBewar

drivers/FileSR.py

@@ -543,6 +543,7 @@ def load(self, vdi_uuid) -> None:
                 self.sm_config_override = {'vhd-parent': self.parent}
             else:
                 self.sm_config_override = {'vhd-parent': None}
+            self.sm_config_override["image-format"] = getImageStringFromVdiType(self.vdi_type)
             return
 
         try:
@@ -593,6 +594,7 @@ def load(self, vdi_uuid) -> None:
                 else:
                     self.parent = ""
                     self.sm_config_override = {'vhd-parent': None}
+                self.sm_config_override["image-format"] = getImageStringFromVdiType(self.vdi_type)
                 self.size = image_info.sizeVirt
                 self.hidden = image_info.hidden
                 if self.hidden: