block/raw-posix: Strip "file:" prefix on creation

The bdrv_create() implementation of the block/raw-posix "file" protocol
driver should strip the "file:" prefix from filenames if present.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Benoit Canet <benoit@irqsave.net>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/raw-posix.c

@@ -1241,6 +1241,8 @@ static int raw_create(const char *filename, QEMUOptionParameter *options,
     int result = 0;
     int64_t total_size = 0;
 
+    strstart(filename, "file:", &filename);
+
     /* Read out options */
     while (options && options->name) {
         if (!strcmp(options->name, BLOCK_OPT_SIZE)) {