main: handle exceptions during startup
main: handle exceptions during startup

If we don't, std::terminate() causes a core dump, even though an
exception is sort-of-expected here and can be handled.

Add an exception handler to fix.

Fixes #1379.
Message-Id: <6949e45a427872bcb5f8f42858dd948abddeafa4@scylladb.com>

kjniemi/scylla,scylladb/scylla,avikivity/scylla,duarten/scylla,duarten/scylla,raphaelsc/scylla,avikivity/scylla,raphaelsc/scylla,scylladb/scylla,avikivity/scylla,scylladb/scylla,duarten/scylla,kjniemi/scylla,kjniemi/scylla,raphaelsc/scylla,scylladb/scylla