Use execvpe instead of execve in omnitrace-sample (#187)

* Use execvpe instead of execve in omnitrace-sample

- previous implementation preferred exe in PATH over exe in PWD
- 'p' variants of exec duplicate the actions of the shell in searching for an executable file if the specified filename does not contain a slash character

* OpenMPI oversubscribe arg in testing

source/bin/omnitrace-sample/impl.cpp

@@ -64,12 +64,6 @@ auto updated_envs  = std::set<std::string_view>{};
 auto original_envs = std::set<std::string>{};
 }  // namespace
 
-std::string
-get_command(const char* _argv0)
-{
-    return omnitrace::path::find_path(_argv0, 0, omnitrace::common::get_env("PATH", ""));
-}
-
 std::string
 get_realpath(const std::string& _v)
 {