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/auth/clean.sh

@@ -13,3 +13,4 @@ rm -f */named.conf
 rm -f dig.out.test*
 rm -f ns2/example.com.bk
 rm -f ns2/example.net.bk
+rm -f ns*/managed-keys.bind*