When loading data using LOAD DATA, it is possible to specify values for
columns using the SET clause (LOAD DATA ... SET col1 = 'foo';).
This can for instance be used to set values for columns that does not
have any data specified in the data file. Intuivetly, it should be
possible to set values for NOT NULL columns with this syntax
(a kind of default value for the column). This did not work with
GEOMETRY NOT NULL columns, as the check for whether or not all columns
had a value assigned to it did not consider columns in the SET clause.
This patch changes this so that columns set in the SET clause are
considered when evaluating whether or not all NOT NULL columns has a
value assigned to it.

Change-Id: I3ca2ffa27ca4fbc6a81723b29188b1c018093e36