Currently starting and stopping of b.m. is spread over main(). Keep it
close to each other.
Another trickery here is that calling b.m.::start() can only be done
after joining the cluster, because this start() spawns replay loop
which, in turn calls token_metadata::count_normal_token_owners() and if
the latter returns zero, the b.m. code uses it as a fraction denominator
and crashes.
With the above in mind, cql_test_env should start batchlog manager after
it "joins the ring" too. For now it doesn't make any difference, but
next patch will make use of it.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
512465288f