srm: Add an access log

Adds an access log to the SRM. The access log writes a line to
/var/log/dcache/access-DOMAIN.log for each SRM access. The log
is rotated once a day and kept for 30 days. Log level and age
can be adjusted through the new properties dcache.log.level.access
and dcache.log.access.max-history. Currently only the SRM supports
this log file, but it is invisioned that other doors could
produce similar logs. Note that an access log file is generated
for every domain, but only domains with an srm service will write
anything to the file. The log format follows the NetLogger format.
Currently, only SRM v2 requests are logged.  IMPORTANT: To allow
dcache to generate the log file the /var/log/dcache directory will
be changed to dcache upon upgrade.

We have regularly found ourselves in the position of not knowing
whether some particular problem is to be attributed to the client
or the server. An access log which for each SRM request shows
some basic information would help alot in such situations.

I tried to keep the format generic enough that we could implement
similar functionality for other doors. Therefore I chose the
NetLogger format. The Common Logging Format used by web servers
does not apply to the kind of informatio I want to log.

The fields to be logged are a tradeoff between logging something
that is useful, but without logging too much or to log something
that can readily be extracted from the SRM database. Hence I
log client IP, DN, session, request method, request token if
available, surl if request token is not available, the return
status and the user-agent. More detailed information about
requests can often be found by looking up the request using the
request token.

Note that I had a change of heart regarding overship of the log
directory. I have always insisted on the directory to not be
writable by the dcache user, but concluded it is just too much
trouble for the default setup. A site that wants the extra
protection against log tampering can still customize their
setup. Our new default is no different from how other services
are setup by default on various distros. As a consequence of
that change I have also moved the events log to the log directory.
The events log too uses a rolling appender, but with a history
of 0 days (so it should delete log files after one day).

I adjusted the name of the events logger such that it too is
placed under the org.dcache hierarchy. Finally I adjusted the
timestamp to include the timezone (per NetLogger recomendations).

A few SRM status codes have been reclassified to not be errors.

The srmLs implementation has been altered to return a request
token no matter what. This is useful no matter whether the request
is processed synchronously or asynchronously as it bind the request
to the request identifier used in the database. I also remove
a useless status string for the ls implementation that I found
while looking at the access log output.

Target: trunk
Request: 2.7
Require-notes: yes
Require-book: yes
Acked-by: Paul Millar <paul.millar@desy.de>
Patch: http://rb.dcache.org/r/6226/