s4 dns_server Bind9: Log opertion durations

s4 dns_server Bind9: Log opertion durations

Add duration debug logging to the samba bind9 dlz driver and the
dnsserver_common routines.  This should aid future diagnosis of
performance issues, and could be used to monitor DNS performance.

The logs are currently Human readable text only, i.e. no JSON formatted
output.

Log lines are of the form:

<function>: DNS timing: result: [<result>] \
duration: (<duration>) zone: [<zone>] name: [<name>] \
data: [<data>]

e.g.

dns_common_wildcard_lookup: DNS timing: result: [WERR_OK] \
duration: (111) zone: [] \
name: [DC=_ldap._tcp.Default-First-Site-Name._sites.ForestDnsZones,\
DC=chgdcpassword.samba.example.com,CN=MicrosoftDNS,DC=DomainDnsZones,\
DC=chgdcpassword,DC=samba,DC=example,DC=com] data: []

Enabled by setting log level to "dns:10"

durations are in microseconds.

Signed-off-by: Gary Lockyer <gary@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Autobuild-User(master): Andrew Bartlett <abartlet@samba.org>
Autobuild-Date(master): Tue May  7 05:03:26 UTC 2019 on sn-devel-184