(BKR-1155) Add a Prefered SSH Connection Method

BKR-834 made vmhostname the default lookup method for SSH connections but this
broke hypervisors which don't have DNS support e.g. OpenStack.  By setting the
connection method in the hypervisor we can choose where to prefer specific
methods.

lib/beaker/hypervisor/vmpooler.rb

@@ -243,6 +243,10 @@ module Beaker
           @logger.debug "No disks to add for #{hostname}"
         end
       end
+
+      # Override SSH connection method if not already explicitly configured.
+      # IP addresses can change across reboots with vmpooler so prefer DNS based resolution
+      @hosts.each {|h| h[:connection_method] ||= 'vmhostname'}
     end
 
     def cleanup
@@ -352,4 +356,4 @@ module Beaker
       disk_added?(parsed[hostname], disk_size, index)
     end
   end
-end
+end