Revert "bitbake.conf: DISTRO_FEATURES as overrides"

Revert "bitbake.conf: DISTRO_FEATURES as overrides"

This reverts commit 3b3ae91a22d6f685e804df4f32cdeebe1bd6bd88.

It turned out that the code which expands DISTRO_FEATURES early during
base config parsing can fail because some entries in DISTRO_FEATURES
might call Python functions like base_conditional() from base.bbclass
which aren't defined yet.

A different solution will be needed.

Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>