If the user enabled multiple experiments, it does not make sense to
execute them concurrently. Therefore, we now only register all enabled
experiments and choose one experiment on fail-client startup. For this
selection, the user can either set the FAIL_EXPERIMENT environment
variable or invoke the tool with a specific argv[0]. For the
bin/-folder, we create symlinks for this mechanism.
With this change, the generic-tracing and generic-experiment can be
compiled into the same executable and we could distribute a "standard"
version of FAIL*.