MDEV-9278 - Debian: the Lintian complains about "shlib-calls-exit" in ha_spider.so

Handlersocket handles errors in a way that it aborts program execution. In most
cases it is done via abort(). One exception was host/service resolution failure,
which was aborted with exit().

As a workaround replaced this exit() with abort() for symmetry with other error
handling.