Increase default max_connections for MySQL from 1024 to 4096

As a matter of fact it seems that the 1024 connections barrier
can easily be reached with modern hardware, see:
https://bugzilla.redhat.com/show_bug.cgi?id=1240824

Change-Id: I194a0dd725907350ca16ea3c41f3ed4f68a11bcf

controller.yaml

@@ -256,7 +256,7 @@ parameters:
   MysqlMaxConnections:
     description: Configures MySQL max_connections config setting
     type: number
-    default: 1024
+    default: 4096
   MysqlRootPassword:
     type: string
     hidden: true

overcloud-without-mergepy.yaml

@@ -413,7 +413,7 @@ parameters:
   MysqlMaxConnections:
     description: Configures MySQL max_connections config setting
     type: number
-    default: 1024
+    default: 4096
   NeutronDnsmasqOptions:
     default: 'dhcp-option-force=26,1400'
     description: Dnsmasq options for neutron-dhcp-agent. The default value here forces MTU to be set to 1400 to account for the tunnel overhead.

puppet/controller-puppet.yaml

@@ -261,7 +261,7 @@ parameters:
   MysqlMaxConnections:
     description: Configures MySQL max_connections config setting
     type: number
-    default: 1024
+    default: 4096
   MysqlRootPassword:
     type: string
     hidden: true