Made more use of castor::utils::errnoToString() and castor::utils::serrnoToString()

castor/legacymsg/RmcProxyTcpIp.hpp

castor/tape/tapeserver/daemon/ProcessForker.cpp

castor/tape/tapeserver/daemon/ProcessForkerProxySocket.cpp

castor/tape/tapeserver/daemon/ProcessForkerUtils.cpp

castor/tape/tapeserver/daemon/TapeDaemon.cpp

castor/tape/tapeserver/daemon/TpconfigLines.cpp

castor/tape/tapeserver/daemon/VdqmConnectionHandler.cpp