fix(linstorvhdutil): coalesce helper returns the sector count now

Without this change we have an error in cleanup.py that interrupts
the coalesce algorithm.

Signed-off-by: Ronan Abhamon <ronan.abhamon@vates.fr>

Author: Wescoeur

drivers/linstor-manager

@@ -539,8 +539,7 @@ def set_parent(session, args):
 def coalesce(session, args):
     try:
         device_path = args['devicePath']
-        vhdutil.coalesce(device_path)
-        return ''
+        return str(vhdutil.coalesce(device_path))
     except Exception as e:
         util.SMlog('linstor-manager:coalesce error: {}'.format(e))
         raise

drivers/linstorvhdutil.py

@@ -376,7 +376,7 @@ def force_parent(self, path, parentPath, parentRaw=False):
 
     @linstormodifier()
     def force_coalesce(self, path):
-        return self._call_method(vhdutil.coalesce, 'coalesce', path, use_parent=True)
+        return int(self._call_method(vhdutil.coalesce, 'coalesce', path, use_parent=True))
 
     @linstormodifier()
     def force_repair(self, path):