schema_builder: Replace type when re-dropping column
schema_builder: Replace type when re-dropping column

Fixes #2634

Signed-off-by: Duarte Nunes <a60e8b7496f7715d71354fe4c06dd24017025bf1@scylladb.com>
Message-Id: <20170725183933.5311-1-a60e8b7496f7715d71354fe4c06dd24017025bf1@scylladb.com>

avikivity/scylla,duarten/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla,scylladb/scylla,avikivity/scylla,duarten/scylla,scylladb/scylla,duarten/scylla