[bugfix] Define HAVE_METIS in config.h when the package is found.
Currently, when the METIS package is found then no HAVE_METIS variable is defined in config.h This MR fixes this issue. I suggest a backport to 2.5
Currently, when the METIS package is found then no HAVE_METIS variable is defined in config.h This MR fixes this issue. I suggest a backport to 2.5