Core: switch user after Bind port.
Core: switch user after Bind port.

When running in newer systems with Kernel >= 3.9 and the SO_REUSEPORT
option is used, the server was switching to the unpriviledge user before
to bind the TCP port, this was generating problems when the port was <= 1024.

Signed-off-by: Eduardo Silva <81f705dc2ce1a61a2621e0e4b442a9474e1d0c70@monkey.io>

sujayraaj/monkey,sujayraaj/monkey_rtems,monkey/monkey,sujayraaj/monkey_rtems,monkey/monkey,sujayraaj/monkeyTest,dougsko/monkey,dougsko/monkey,WilliamRen/monkey-1,sbagmeijer/monkey,sujayraaj/monkey_rtems,sujayraaj/monkeyTest,sujayraaj/monkeyTest,sujayraaj/monkey_rtems,dreamsxin/monkey,monkey/monkey,WilliamRen/monkey-1,sbagmeijer/monkey,WilliamRen/monkey-1,dougsko/monkey,sbagmeijer/monkey,WilliamRen/monkey-1,WilliamRen/monkey-1,sujayraaj/monkey,dougsko/monkey,dreamsxin/monkey,dreamsxin/monkey,monkey/monkey,sbagmeijer/monkey,monkey/monkey,sujayraaj/monkey,dreamsxin/monkey,sujayraaj/monkey,sbagmeijer/monkey,sujayraaj/monkey_rtems,dougsko/monkey,dreamsxin/monkey,sujayraaj/monkey,monkey/monkey,sujayraaj/monkeyTest