The memory leak was caused by not freeing the shadow context the firewall
child process uses for logging.  In addition this child process had a
connection to the database open as well, which was not needed.  This
connection is now disconnected immediately after the child process has
started.

Added also usage of mlock() to protect sensitive information from being
swapped out to disk.

This has two purposes.  To make the code more readable and to use the
same maximum length of the data being retrieved from the environment table.

This only affects functions related to MAC address and certificate depth

This is a follow up of commit 80b41e27b7361633bee17c64bbb95490dc94ab9f

The eDBopen_session_seed() function was prune to an integer overflow issue, if
the input data (some which comes from clients) exeeds the size_t max value which
calloc() uses (via malloc_nullsafe()).  The totlen variable was in addition defined
as int and the totlen value was multiplied by 2.

The fix was to use the maximum values used when calling get_env().  These values the
maximum can then be added together to retrieve the maximum length of the seeddata string.
This should also make the execution go slightly quicker as strlen_nullsafe() is no
longer called for each of the input variables.  In addition, there are no reasons to
multiply the totlen value by two as it did.

Credit goes to Larry Highsmith for noticing this potential problem.