Use node namespace for pr2_etherCAT instead of hardcoded value (ros ticket #4992)

[ahendrix]

from pr2_etherCAT/src/main.cpp :
{{{
static const std::string name = "pr2_etherCAT";
}}}

trac data:

• Owner: wheeler
• Reporter: dking
• Reported at: Mon Jan 24 10:59:23 2011
• URL: https://code.ros.org/trac/wg-ros-pkg/ticket/4992