this module deals with queueing servers that samba must sync browse
lists with. it will always issue a name query immediately before
actually carrying out the NetServerEnum call, to ensure that time
is not wasted by a remote server's failure.

this module was created to minimise the amount of NetServerEnum calls
that samba may be asked to perform, by maintaining the name of a server
for up to a minute after the NetServerEnum call was issued, and
disallowing further NetServerEnum calls to this remote server until
the entry is removed.

samba can ask for a NetServerEnum call to be issued to grab a remote
server's list of servers and workgroups either in its capacity as
a primary domain controller (domain master browser), as a local
master browser.

samba does not deal with becoming a backup master browser properly
at present.


/*************************************************************************
  do_browser_lists()
  *************************************************************************/

this function is responsible for finding an appropriate entry in the
sync browser cache, initiating a name query (which results in a
NetServerEnum call if there is a positive response), and then
removing all entries that have been actioned and have been around
for over a minute.


/*************************************************************************
  start_sync_browse_entry()
  *************************************************************************/

this function is responsible for initiating a name query. if a
positive response is received, then this will result in a
NetServerEnum api call.

samba will only initiate this process if it is a master browser
for this workgroup.


/*************************************************************************
  add_browser_entry()
  *************************************************************************/

this function is responsible for adding a browser into the list of
servers to sync browse lists with. if the server entry has already
been added and syncing browse lists has already been initiated, it
will not be added again.


/*************************************************************************
  expire_browse_cache()
  *************************************************************************/

this function is responsible for removing entries that have had the
sync browse list initiated (whether that succeeded or not is beyond
this function's scope) and have been in the cache for a while.


/*************************************************************************
  add_browse_entry()
  *************************************************************************/

this function is responsible for adding a new entry into the list
of servers to sync browse lists with at some point in the near future.