rafs: unify error code

Based on the error definition, InvalidData is preferable than InvalidInput.

Data not valid for the operation were encountered.
Unlike [InvalidInput], this typically means that the operation parameters were valid, however the error was caused by malformed input data.
For example, a function that reads a file into a string will error with InvalidData if the file's contents are not valid UTF-8.

Signed-off-by: Liu Bo <liub.liubo@gmail.com>

Author: liubogithub

api/src/config.rs

@@ -124,7 +124,7 @@ impl ConfigV2 {
     pub fn get_backend_config(&self) -> Result<&BackendConfigV2> {
         self.backend.as_ref().ok_or_else(|| {
             Error::new(
-                ErrorKind::InvalidInput,
+                ErrorKind::InvalidData,
                 "no configuration information for backend",
             )
         })
@@ -163,7 +163,7 @@ impl ConfigV2 {
     pub fn get_rafs_config(&self) -> Result<&RafsConfigV2> {
         self.rafs.as_ref().ok_or_else(|| {
             Error::new(
-                ErrorKind::InvalidInput,
+                ErrorKind::InvalidData,
                 "no configuration information for rafs",
             )
         })