Add file write check for WRITE permission

[Hackndo]

Currently smbmap checks if it can create a directory in a remote share to check if the user has WRITE permission. The issue is that a share can restrict write permission to create files only, but not create directories. Here is an example:

Thus if creating an empty dir fails, smbmap shouldn't stop there and should try and create an empty file with minimal permissions (FILE_WRITE_DATA).

This pull request adds this feature to limit the number of false negative.

Before:

After:

(PS: These screenshots are using hackthebox RE box, which is retired, so it is not a spoil as the solution for this box has been officially released)

[Hackndo]

@ippsec detailed the issue here https://youtu.be/YXAakamjO_I?t=467

[ShawnDEvans]

This is awesome! I hadn't realized there was a permissions distinction between file write and directory write.