libkas: Add /sbin and /usr/sbin to PATH

/sbin and /usr/sbin might contain tools Yocto depens on, e.g. 'ip'.

"""
The following required tools (as specified by HOSTTOOLS) appear to be
unavailable in PATH, please install them in order to proceed:

	ip
"""

Signed-off-by: Daniel Wagner <daniel.wagner@siemens.com>

kas/libkas.py

@@ -291,7 +291,7 @@ def get_build_environ(config, build_dir):
     os.chmod(get_bb_env_file, 0o775)
 
     env = {}
-    env['PATH'] = '/bin:/usr/bin'
+    env['PATH'] = '/usr/sbin:/usr/bin:/sbin:/bin'
 
     (_, output) = run_cmd([get_bb_env_file, build_dir],
                           cwd=init_repo.path, env=env, liveupdate=False)