Remove misplaced parathesis (sysctl check)

#### Before

````
jan@himinbjorg:~$ riak-admin diag
Attempting to restart script through sudo -H -u riak
11:00:52.982 [critical] vm.swappiness is 60, should be no more than 0)
11:00:52.982 [critical] net.core.wmem_default is 229376, should be at least 8388608)
11:00:52.982 [critical] net.core.rmem_default is 229376, should be at least 8388608)
11:00:52.982 [critical] net.core.wmem_max is 131071, should be at least 8388608)
11:00:52.982 [critical] net.core.rmem_max is 131071, should be at least 8388608)
11:00:52.982 [critical] net.core.netdev_max_backlog is 1000, should be at least 10000)
11:00:52.982 [critical] net.core.somaxconn is 128, should be at least 4000)
11:00:52.983 [critical] net.ipv4.tcp_max_syn_backlog is 2048, should be at least 40000)
11:00:52.983 [critical] net.ipv4.tcp_fin_timeout is 60, should be no more than 15)
11:00:52.983 [critical] net.ipv4.tcp_tw_reuse is 0, should be 1)
...
````

#### After

````
jan@himinbjorg:~$ riak-admin diag
Attempting to restart script through sudo -H -u riak
11:00:52.982 [critical] vm.swappiness is 60, should be no more than 0
11:00:52.982 [critical] net.core.wmem_default is 229376, should be at least 8388608
11:00:52.982 [critical] net.core.rmem_default is 229376, should be at least 8388608
11:00:52.982 [critical] net.core.wmem_max is 131071, should be at least 8388608
11:00:52.982 [critical] net.core.rmem_max is 131071, should be at least 8388608
11:00:52.982 [critical] net.core.netdev_max_backlog is 1000, should be at least 10000
11:00:52.982 [critical] net.core.somaxconn is 128, should be at least 4000
11:00:52.983 [critical] net.ipv4.tcp_max_syn_backlog is 2048, should be at least 40000
11:00:52.983 [critical] net.ipv4.tcp_fin_timeout is 60, should be no more than 15
11:00:52.983 [critical] net.ipv4.tcp_tw_reuse is 0, should be 1
...
````