postinst_intercepts: add a delay_to_first_boot hook

This allows postinsts scripts to explicitly request a deferral to first boot
(by calling 'postinst_intercept delay_to_first_boot') instead of 'exit 1' which
should be used only to indicate actual script failures.

(From OE-Core rev: 853ac4a061e47c70b61e255c3cf6109d2058d2cc)

Signed-off-by: Alexander Kanavin <alexander.kanavin@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/postinst-intercepts/delay_to_first_boot

@@ -0,0 +1,2 @@
+#!/bin/sh
+exit 1