Set PYTHONUNBUFFERED for systemd managed python

This lets python scripts print to the journal.

Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/common/recipes-phosphor/rest-dbus/files/rest-dbus.service b/common/recipes-phosphor/rest-dbus/files/rest-dbus.service
index 5ad582f..d3bddab 100644
--- a/common/recipes-phosphor/rest-dbus/files/rest-dbus.service
+++ b/common/recipes-phosphor/rest-dbus/files/rest-dbus.service
@@ -4,3 +4,4 @@
 [Service]
 Restart=always
 ExecStart=/usr/sbin/rest-dbus
+Environment="PYTHONUNBUFFERED=1"