CVE-2019-3824 ldb: wildcard_match check tree operation

CVE-2019-3824 ldb: wildcard_match check tree operation

Check the operation type of the passed parse tree, and return
LDB_INAPPROPRIATE_MATCH if the operation is not LDB_OP_SUBSTRING.

A query of "attribute=*" gets parsed as LDB_OP_PRESENT, checking the
operation and failing ldb_wildcard_match should help prevent confusion
writing tests.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13773

Signed-off-by: Gary Lockyer <gary@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>