bitbake: bitbake & hob: reparse config files, when sanity check updates bblayers...

bitbake: bitbake & hob: reparse config files, when sanity check updates bblayers.conf

I've sent a patch to poky, with some changes in sanity.bbclass. When bblayers.conf
is updated, it updates also a variable to know when to reparse configuration files.
This patch contains the changes to reparse conf files, after a sanity check which
changes bblayers.conf.

[YOCTO #3213]
(Bitbake rev: 966e3e59ceb1c8b33b5881f291c148ea6513eda0)

Signed-off-by: Cristiana Voicu <cristiana.voicu@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>