When the secondary index code builds a "%s IS NOT NULL" clause for a
CQL statement, it needs to quote the column name if it needs to be
(not only lowercase, digits and _).
Fixes #3401.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20180429221857.6248-7-nyh@scylladb.com>
(cherry picked from commit 46d4f6f352)