rcutorture: Fix bug in reporting Kconfig mis-settings

Kconfig "select" clauses can defeat Kconfig-fragment file attempts to
clear a given Kconfig variable, and dependencies can defeat attempts to
set a given Kconfig variable.  Because "select" clauses and dependencies
can be added at any time, there needs to be a way to verify that the
Kconfig-fragment file's requests were honored.  And there is, except
that it is buggy.  This commit therefore provides the needed fix.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>