Push the expanduser call on the source down to slurp rather than fetch

Also moves the calculation of the destination file name until after
the slurp of the file contents, since the source as returned by slurp
may now be different, so we want to use that expanded path locally.

Fixes #8942

library/network/slurp

@@ -57,7 +57,7 @@ def main():
         ),
         supports_check_mode=True
     )
-    source = module.params['src']
+    source = os.path.expanduser(module.params['src'])
 
     if not os.path.exists(source):
         module.fail_json(msg="file not found: %s" % source)
@@ -66,7 +66,7 @@ def main():
 
     data = base64.b64encode(file(source).read())
 
-    module.exit_json(content=data, encoding='base64')
+    module.exit_json(content=data, source=source, encoding='base64')
 
 # import module snippets
 from ansible.module_utils.basic import *