(POOLER-160) Revise connection metrics

The redis pooler connection metric used "metric_prefix" which is
misleading, so split this into connpool_type and connpool_provider.
Also remove some earlier jruby compatibility code to reduce
rebase conflicts when this is rebased on top of Matt's changes.

lib/vmpooler/providers/dummy.rb

@@ -29,7 +29,8 @@ module Vmpooler
           logger.log('d', "[#{name}] ConnPool - Creating a connection pool of size #{connpool_size} with timeout #{connpool_timeout}")
           @connection_pool = Vmpooler::PoolManager::GenericConnectionPool.new(
             metrics: metrics,
-            metric_prefix: "#{name}_provider_connection_pool",
+            connpool_type: 'provider_connection_pool',
+            connpool_provider: name,
             size: connpool_size,
             timeout: connpool_timeout
           ) do