Don't execute code from the plugin in config tool

[davidben]

Using dlopen executes some code from it, and distributions run that tool as root. May as well avoid it and find some ELF parsing utilities to check for symbol existence.

[davidben]

We're actually much better about this than I thought. I believe only code from assumed wrapper plugins gets executed, so npwrapper.FOO.so and some other things. Some refactoring can probably make this a little better. Main difficulty is that ELF-munging code cannot read data, so it needs to dlopen, but it does so a bit more readily than it should