automated: linux: use default token with lmp-device-register

If LmP is configured with auto-registration, there should be a default
token available on the device. With this patch lmp-device-register test
uses the default token avoiding exposing it through test job.

Signed-off-by: Milosz Wasilewski <milosz.wasilewski@foundries.io>

automated/linux/lmp-device-register/lmp-device-register.sh

@@ -39,8 +39,12 @@ fi
 
 # quit if token is not provided
 if [ -z "${TOKEN}" ]; then
-    # exit the test
-    error_fatal "Token not provided"
+	if [ -f /etc/lmp-device-register-token ]; then
+		TOKEN=$(head -n1 /etc/lmp-device-register-token)
+	else
+	    # exit the test
+    	error_fatal "Token not provided"
+	fi
 fi
 
 if [ -z "${REG_UUID}" ]; then