[master] Added ccpcheck suppression to pgsql_lease_mgr.cc

Suppressed an unused structure member complaint in dhcpsrv/psql_lease_mgr.cc
This code is going to get a makeover under 3382 and it will be more properly
addressed then.

src/lib/dhcpsrv/pgsql_lease_mgr.cc

@@ -42,6 +42,7 @@ struct TaggedStatement {
 
     /// Query index
     /// @todo cppcheck flags index as unused
+    // cppcheck-suppress unusedStructMember
     PgSqlLeaseMgr::StatementIndex index;
 
     /// Number of parameters for a given query