bitbake: bitbake-getvar: skip info output of bitbake for quiet

Calling oe-debuginfod in a build failed:
...
$ oe-debuginfod
|Getting sysroot...
|Error: NOTE: Reconnecting to bitbake server...
|NOTE: Retrying server connection (#1)... (18:55:53.009687)
|path-to-build/tmp/work/x86_64-linux/elfutils-native/0.192/recipe-sysroot-native doesn't exist.
|Have you run 'bitbake elfutils-native -caddto_recipe_sysroot'?
...

The script oe-debuginfod calls bitbake-getvar to get sysroot, the
output of bitbake-getvar was mixed with info output of bitbake
...
NOTE: Reconnecting to bitbake server...
NOTE: Retrying server connection (#1)... (18:55:53.009687)
...

Set logger level to logging.WARNING to skip info output
for quiet

(Bitbake rev: 873c524e1a33846df8f34b7c87b298349277b3d5)

Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/bin/bitbake-getvar

@@ -10,6 +10,7 @@ import io
 import os
 import sys
 import warnings
+import logging
 warnings.simplefilter("default")
 
 bindir = os.path.dirname(__file__)
@@ -38,6 +39,10 @@ if __name__ == "__main__":
             sys.exit("--flag only makes sense with --value")
 
     quiet = args.quiet or args.value
+    if quiet:
+        logger = logging.getLogger("BitBake")
+        logger.setLevel(logging.WARNING)
+
     with bb.tinfoil.Tinfoil(tracking=True, setup_logging=not quiet) as tinfoil:
         if args.recipe:
             tinfoil.prepare(quiet=3 if quiet else 2)