cql3: Replace count_if with find_atom
cql3: Replace count_if with find_atom

count_if finds all matching atoms, which is redundant when we only
want to find one.

Signed-off-by: Dejan Mircevski <1e9694aae17a51d4875d9bf4a0d0e20ef37c1b85@scylladb.com>

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla