git-submodule.sh: Modern shell scripting (use $() instead of ``)

Various shell files contain a mix between obsolete ``
and modern $(); It would be nice to convert to using $()
everywhere.

Signed-off-by: Mao Zhongyi <maozhongyi@cmss.chinamobile.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

scripts/git-submodule.sh

@@ -59,8 +59,8 @@ status)
     fi
 
     test -f "$substat" || exit 1
-    CURSTATUS=`$GIT submodule status $modules`
-    OLDSTATUS=`cat $substat`
+    CURSTATUS=$($GIT submodule status $modules)
+    OLDSTATUS=$(cat $substat)
     test "$CURSTATUS" = "$OLDSTATUS"
     exit $?
     ;;