vs_bridge: Ensure "exists?" returns true

... instead of nothing.

Change-Id: Ifd943f99a7b0a7d12170e773ffd02bd61a0eb2bc
(cherry picked from commit 35d4713eae88881740e9a8b0eaad843d989dd5ad)

lib/puppet/provider/vs_bridge/ovs.rb

@@ -6,6 +6,7 @@ Puppet::Type.type(:vs_bridge).provide(:ovs) do
 
   def exists?
     vsctl("br-exists", @resource[:name])
+    return true
   rescue Puppet::ExecutionFailure
     return false
   end