Fix #4119 - SMB lost search ID (sid) in find_first method

This will fix issue #4119. A bug in the find_first method in rex
SMB.

When the SMB client requests a TRANS2_FIND_FIRST2 for retriving
information about what items a directory has, the server returns
a response that contains an SID - a search identifier for the
transaction. If the SMB client wants more data, it must send a
TRANS2_FIND_NEXT2 request with the same SID. And then the server
will continue sending more until it runs out.

The root cause of this bug is that after the TRANS2_FIND_FIRST2
request is sent, our SMB's find_first method forgets the SID at
the end of the loop (out of scope).
Land #4173, @wchen-r7's fix for SMB find_first

* Fixes #4119, SMB find_first("\\*") does not return accurate results
* It missed initialization of sid