managed_bytes: Delete dead 'if'
managed_bytes: Delete dead 'if'

If external is true, _u.ptr is not null. An empty managed_bytes uses
the internal representation.

The current code looks scary, since it seems possible that backref
would still point to the old location, which would invite corruption
when the reclaimer runs.

Signed-off-by: Rafael Ávila de Espíndola <1975039f9046bf513b77c0c5639a0efc25f00e7f@scylladb.com>
Reviewed-by: Benny Halevy <23c997c90eb8537635e9392d48e7af1bf1b2ca22@scylladb.com>
Message-Id: <20200716233124.521796-1-1975039f9046bf513b77c0c5639a0efc25f00e7f@scylladb.com>

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