This patch does two things:
1) For SMB close requests, tear down any associated DCE-RPC
analyzer if one exists.
2) Protect from fid_to_analyzer_map growing unbounded by introducing a
new SMB::max_dce_rpc_analyzers limit and forcefully wipe the
analyzers if exceeded. Propagate this to script land as event
smb_discarded_dce_rpc_analyzers() for additional cleanup.
This is mostly to fix how the binpac SMB analyzer tracks individual
DCE-RPC analyzers per open fid. Connections that re-open the same or
different pipe may currently allocate unbounded number of analyzers.
Closes#3145.