kernel/v2: allow private network type to be a string [GH-3349]

CHANGELOG.md

@@ -14,6 +14,8 @@ BUG FIXES:
   - core: Removing a specific box version that doesn't exist doesn't
       crash Vagrant. [GH-3364]
   - core: SSH commands are forced to be ASCII.
+  - core: private networks with DHCP type work if type parameter is
+      a string and not a symbol. [GH-3349]
   - commands/status: Machine readable output contains the target. [GH-3218]
   - guests/debian: Changing host name works properly. [GH-3283]
   - guests/suse: Shutdown works correctly on SLES [GH-2775]

plugins/kernel_v2/config/vm.rb

@@ -578,7 +578,7 @@ module VagrantPlugins
           end
 
           if type == :private_network
-            if options[:type] != :dhcp
+            if options[:type].to_sym != :dhcp
               if !options[:ip]
                 errors << I18n.t("vagrant.config.vm.network_ip_required")
               end