hosts/bsd: make directories unique when exporting

CHANGELOG.md

@@ -88,6 +88,8 @@ BUG FIXES:
     [GH-2792]
   - hosts/bsd: Don't invoke shell for NFS sudo calls. [GH-2808]
   - hosts/bsd: Sort NFS exports to avoid false validation errors. [GH-2927]
+  - hosts/bsd: No more checkexports NFS errors if you're sharing the
+    same directory. [GH-3023]
   - hosts/gentoo: Look for systemctl in `/usr/bin` [GH-2858]
   - hosts/linux: Properly escape regular expression to prune NFS exports,
     allowing VMware to work properly. [GH-2934]

plugins/hosts/bsd/cap/nfs.rb

@@ -50,8 +50,10 @@ module VagrantPlugins
           end
 
           # Sort all the keys by length so that the directory closest to
-          # the root is exported first.
+          # the root is exported first. Also, remove duplicates so that
+          # checkexports will work properly.
           dirmap.each do |dirs, _|
+            dirs.uniq!
             dirs.sort_by! { |d| d.length }
           end