The license for the impacket package was not in our tree.

Imported now from upstream's
https://github.com/SecureAuthCorp/impacket/blob/master/LICENSE

Reported-by: infinnovation-dev on github
Fixes #3276
Closes #3277

Detected by Coverity Analysis:

Error: IDENTIFIER_TYPO:
curl-7.58.0/tests/python_dependencies/impacket/spnego.py:229: identifier_typo: Using "SuportedMech" appears to be a typo:
* Identifier "SuportedMech" is only known to be referenced here, or in copies of this code.
* Identifier "SupportedMech" is referenced elsewhere at least 4 times.
curl-7.58.0/tests/python_dependencies/impacket/smbserver.py:2651: identifier_use: Example 1: Using identifier "SupportedMech".
curl-7.58.0/tests/python_dependencies/impacket/smbserver.py:2308: identifier_use: Example 2: Using identifier "SupportedMech".
curl-7.58.0/tests/python_dependencies/impacket/spnego.py:252: identifier_use: Example 3: Using identifier "SupportedMech" (2 total uses in this function).
curl-7.58.0/tests/python_dependencies/impacket/spnego.py:229: remediation: Should identifier "SuportedMech" be replaced by "SupportedMech"?

Closes #2379

Add test 1451 which does some very basic SMB testing using the impacket
SMB server.

Closes #1630

Import impacket 0.9.15 for use in SMB testing. This was generated by
doing "pip2.7 install -t . impacket"

Unnecessary files for current testing were deleted.