oe/types: Allow boolean to accept an existing boolean

Exception: TypeError: boolean accepts a string, not '<class 'bool'>

is a bit annoying if you pass in True/False. Tweak the function
to make it forgive that situation.

(From OE-Core rev: 147f5a665fe5073027d92e4acac631f15f08f79f)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oe/types.py

@@ -105,6 +105,8 @@ def boolean(value):
     Valid values for true: 'yes', 'y', 'true', 't', '1'
     Valid values for false: 'no', 'n', 'false', 'f', '0'
     """
+    if isinstance(value, bool):
+        return value
 
     if not isinstance(value, str):
         raise TypeError("boolean accepts a string, not '%s'" % type(value))