Fix first boot deferral and postinst error reporting

This patchset is aiming to fix long-standing problems with package post-installation scriptlets:

1) The way to defer them to first boot is to issue 'exit 1'. On the other hand, 'exit 1' is also the way to indicate an error in the script. The patches decouple these two things.

2) Scriptlets should be executed using '-e', otherwise failing commands in the middle of the scriptlet will not be reported as such.

3) The patchset also adds a convenient shortcut for deferring scriptlets to first boot execution:

pkg_postinst_ontarget_PACKAGENAME() {
# Actions to carry out on the device go here
....
}

The following changes since commit 0c537554fc2cf58a9cbfeaf39ed918c607483dce:

testimage: enable gi test suite (2018-01-29 10:31:58 +0000)

are available in the Git repository at:

git://git.yoctoproject.org/poky-contrib akanavin/dnf-rpm4-postinst-fix
http://git.yoctoproject.org/cgit.cgi/poky-contrib/log/?h=akanavin/dnf-rpm4-postinst-fix

Alexander Kanavin (7):
postinst_intercepts: add a delay_to_first_boot hook meta/lib/oe/rootfs.py: separate first boot deferral logic into a
separate function
meta/lib/oe/rootfs.py: do not execute defer_to_first_boot when
processing postinst_intercept hooks
package.bbclass: add support for pkg_postinst_ontarget() meta/lib/oe/package_manager.py: deprecate 'exit 1' as a way to defer
to first boot
package_rpm.bbclass: run pre/post installation scriptlets using sh -e rootfs.py: change the notice about deferring scripts to first boot
from warning to a note

 .../recipes-test/postinst/postinst_1.0.bb          | 14 ++------
 meta/classes/package.bbclass                       | 20 +++++++++++
 meta/classes/package_rpm.bbclass                   |  8 ++---
 meta/lib/oe/package_manager.py                     |  3 ++
 meta/lib/oe/rootfs.py                              | 39 +++++++++++++---------
 scripts/postinst-intercepts/delay_to_first_boot    |  2 ++
 6 files changed, 54 insertions(+), 32 deletions(-)
 create mode 100644 scripts/postinst-intercepts/delay_to_first_boot

2.15.1