network: Clean up log output format

Before:

org.kde.ksysguard.plugin.network: Helper process terminated abnormally!
org.kde.ksysguard.plugin.network: "The process doesn't have permission to open the capture source\n"

After:

org.kde.ksysguard.plugin.network: Helper process terminated abnormally: "The process doesn't have permission to open the capture source"

GIT_SILENT