seastar::make_shared has a constructor taking a T&&. There is no such
constructor in std::make_shared:
https://en.cppreference.com/w/cpp/memory/shared_ptr/make_shared
This means that we have to move from
make_shared(T(...)
to
make_shared<T>(...)
If we don't want to depend on the idiosyncrasies of
seastar::make_shared.
Signed-off-by: Rafael Ávila de Espíndola <espindola@scylladb.com>