rewrite logfileconfig system test

the logfileconfig system test did not conform to the style of
other tests, and was difficult to read and maintain. it has
been cleaned up and simplifeid in several ways:

- named.args used when appropriate so that named can be started with
  specified command line arguments, instead of having it launched
  directly from tests.sh
- unused root zone removed from named configuration
- an existing directory used instead of using 'mkdir' to create one
- dnssec-validation disabled to stop the server sending unnecessary queries

incidental fix: removed leftover debugging printfs from logconf.c.

bin/tests/system/logfileconfig/clean.sh

@@ -12,10 +12,9 @@
 #
 # Clean up after log file tests
 #
-rm -f ns1/rndc.conf
-rm -f ns1/controls.conf
 rm -f ns1/named.conf
-rm -f ns1/named.pid ns1/named.run
+rm -f ns1/named.args
+rm -f ns1/named.pid ns1/named.run ns1/named.run.prev
 rm -f ns1/named.memstats ns1/dig.out
 rm -f ns1/named_log ns1/named_pipe ns1/named_sym
 rm -rf ns1/named_dir