git submodule update wrep-lib should prefetch submodule remote

$ git submodule update wsrep-lib

fatal: failed to unpack tree object 12a50c43b112648fec3b1213a1470a85aca55f2c

error: Submodule 'wsrep-API/v26' could not be updated.

error: Cannot update submodule:

        wsrep-API/v26

Aborting

Unable to checkout 'a17b65a25f5e608ffa8e6e051930bf47ed95019a' in submodule path 'wsrep-lib'

{10.5b} midenok@lian:src$ cd wsrep-lib

/home/midenok/src/mariadb/10.5b/src/wsrep-lib

{10.5b} midenok@lian:wsrep-lib$ git fetch

Fetching submodule wsrep-API/v26

From https://github.com/codership/wsrep-API

 * [new branch]      examples   -> origin/examples

 * [new branch]      examples2  -> origin/examples2

 * [new branch]      examples3  -> origin/examples3

 * [new branch]      examples4  -> origin/examples4

 * [new branch]      examples5  -> origin/examples5

 * [new branch]      examples6  -> origin/examples6

   c055535..35b9ece  master     -> origin/master

   eab2d5d..b3c6ea7  v25        -> origin/v25

   75a5f45..12a50c4  v26        -> origin/v26

{10.5b} midenok@lian:wsrep-lib$ cd ..

{10.5b} midenok@lian:src$ git submodule update wsrep-lib

Submodule path 'wsrep-lib': checked out 'a17b65a25f5e608ffa8e6e051930bf47ed95019a'