bitbake: lib/bb/utils: no need to unsetenv when manipulating os.environ

Doing both os.unsetenv(foo) and then del os.environ[foo] is pointless as del
will call unsetenv automatically.

(Bitbake rev: a4463e2ff3c7d234320176d671719243292f1af0)

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/utils.py

@@ -599,7 +599,6 @@ def filter_environment(good_vars):
             continue
 
         removed_vars[key] = os.environ[key]
-        os.unsetenv(key)
         del os.environ[key]
 
     # If we spawn a python process, we need to have a UTF-8 locale, else python's file