When a variable was removed from a configuration file it was not
removed from memory. This also had the effect of not allowing
to set a new value for the same variable with saveConfigurationVar.
(Bitbake rev: 30cd1fab6633aaf50ef53eefccc6d69d598eb293)
Signed-off-by: Marius Avram <marius.avram@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>