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/database/clean.sh

@@ -12,3 +12,4 @@
 rm -f ns1/named.conf ns1/named.run ns1/named.memstats
 rm -f dig.out.*
 rm -f ns*/named.lock
+rm -f ns*/managed-keys.bind*