security/doas: Update to 6.0p1

This update brings the security/doas port up to date with upstream.
This gives us the added benefit of restricted path searching. Which
means if the admin puts a relative path in the doas.conf file, doas
will limit the number of places where the executable can be found.
This prevents users from putting malicious executables with the same
name in their custom path.

PR: 222092
Submitted by: jsmith@resonatingmedia.com (maintainer)
MFH: 2017Q3