Increase tcp_retries2 value

Current value of 5 results in socket operation timeout after ~12.9
seconds. This is a bit too low, e.g. we've seen RabbitMQ network
splits in production.

This 12.9s amount is equal as 0.2*(2^1+2^2+..2^5), where 0.2 is a
retry timeout (RTO) that is calculated by kernel on a per-socket
basis. But in fast local networks it usually almost equal to minimum
values of 0.2s hardcoded in linux kernel (and BTW, RFC says that
minimum value should be 1s).

On the other hand, comment in netconfig.pp says that our target
timeout is ~54 seconds. And changing tcp_retries2 to 7 is consistent
with that comment - tests an live env show that resulting timeout is
~52.2s

Change-Id: Ib52f40ef1017a9da5a29cd62fb744a4597860763

deployment/puppet/osnailyfacter/manifests/netconfig/netconfig.pp

@@ -42,7 +42,7 @@ class osnailyfacter::netconfig::netconfig {
     tcpka_time   => '30',
     tcpka_probes => '8',
     tcpka_intvl  => '3',
-    tcp_retries2 => '5',
+    tcp_retries2 => '7',
   }
 
   # increase network backlog for performance on fast networks

tests/noop/spec/hosts/netconfig/netconfig_spec.rb

@@ -27,7 +27,7 @@ describe manifest do
        'tcpka_time'   => '30',
        'tcpka_probes' => '8',
        'tcpka_intvl'  => '3',
-       'tcp_retries2' => '5',
+       'tcp_retries2' => '7',
     ) }
     it { should contain_sysctl__value('net.core.netdev_max_backlog').with('value' => '261144') }
     it { should contain_class('sysfs') }