enum_shares improved error handling and regex for some cases

[Xhoenix]

• Handle error which occurs when enumerting IPC$ shares.
• Extend regex for cases where the directory listing doesn't have ".." directory in it.

[Xhoenix]

The regex can be simplified to /\n\s+.*?\s+D.*\d{4}\n/

[Xhoenix]

The get_user_details_from_rid() function does not implement check for the initialization of $user_info variable resulting in errors like these when used with the detailed(-d) flag.

While the get_group_details_from_rid() function implements such a check.

[Xhoenix]

The enum_users() function works correctly but as the error NT_STATUS_ACCESS_DENIED is not shown as normal output in some cases it results in those errors mentioned in this issue. Turning up debuglevel upto 10 in rpcclient shows it.

[Xhoenix]

@timb-machine Can you look into this?