base.bbclass: drop now that we're using a poky fork

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
setup-environment: always unset OPTIONALLAYERS

This ensures we never have a remnant OPTIONLLAYERS hanging around from
a different MEL version affecting another.

JIRA: SB-959

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
package.bbcalss: Remove unnecessary package.remove function.

* Package.remove function was causing error when INCOMPATIBLE_LICENSES
was truned on. It was saying str does not have remove function. It was
not neede so removed it.

Signed-off-by: Noor Ahsan <noor_ahsan@mentor.com>