scripts: ensure tinfoil is shut down correctly

We should always shut down tinfoil when we're finished with it, either
by explicitly calling the shutdown() method or by using it as a
context manager ("with ...").

(From OE-Core rev: 5ec6d9ef309b841cdcbf1d14ac678d106d5d888a)

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/devtool

@@ -289,17 +289,15 @@ def main():
 
     if global_args.bbpath is None:
         tinfoil = setup_tinfoil(config_only=True, basepath=basepath)
-        global_args.bbpath = tinfoil.config_data.getVar('BBPATH', True)
-    else:
-        tinfoil = None
+        try:
+            global_args.bbpath = tinfoil.config_data.getVar('BBPATH', True)
+        finally:
+            tinfoil.shutdown()
 
     for path in [scripts_path] + global_args.bbpath.split(':'):
         pluginpath = os.path.join(path, 'lib', 'devtool')
         scriptutils.load_plugins(logger, plugins, pluginpath)
 
-    if tinfoil:
-        tinfoil.shutdown()
-
     subparsers = parser.add_subparsers(dest="subparser_name", title='subcommands', metavar='<subcommand>')
     subparsers.required = True