Remove server logging globals

Remove server logging globals

Remove the global variables used to setup server logging and replace
with an argument to OpenLog.

Keep the LogLevel variable as a global for use by the logging macros,
but provide an inline function for applications which check the log
level to dump more information when the log level is increased.

Provide consistency by adding syslog tags to processes that did not
previously set one (salvageserver, salvager, and volserver).

[kaduk@mit.edu: update commit message, use old-style log rotation for
kalog, minor commenting fixes]

Change-Id: I11cffbdd1418304d33f0be02dd7e600955c4a8bb
Reviewed-on: https://gerrit.openafs.org/12168
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>