bitbake: toaster: use decode('utf-8') for binary data

Decoded binary data to utf-8 to fix the following
error when runnign on python 3:
TypeError: Type str doesn't support the buffer API

[YOCTO #9584]

(Bitbake rev: 752ea00919ef054622a51ce097923309934eff2b)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/toaster/bldcontrol/management/commands/loadconf.py

@@ -54,7 +54,7 @@ class Command(BaseCommand):
             (out,err) = cmd.communicate()
             if cmd.returncode != 0:
                 logging.warning("Error while importing layer vcs_url: git error: %s" % err)
-            for line in out.split("\n"):
+            for line in out.decode('utf-8').split("\n"):
                 try:
                     (name, path) = line.split("\t", 1)
                     if name == remote_name: