update system tests so validation won't fail when using IANA key

- all tests with "recursion yes" now also specify "dnssec-validation yes",
  and all tests with "recursion no" also specify "dnssec-validation no".
  this must be maintained in all new tests, or else validation will fail
  when we use local root zones for testing.
- clean.sh has been modified where necessary to remove managed-keys.bind
  and viewname.mkeys files.

bin/tests/system/runtime/clean.sh

@@ -17,3 +17,4 @@ rm -f *.pid
 rm -f rndc.out*
 [ -d ns2/nope ] && chmod 755 ns2/nope
 rm -rf ns2/nope
+rm -f ns*/managed-keys.bind*