NO_AUTO_VALUE_ON_ZERO mode.

The table->auto_increment_field_not_null variable wasn't reset after
reading a row which may lead to inserting a wrong value to the auto-increment
field to the following row.

The table->auto_increment_field_not_null variable is reset now right after a
row is being written in the read_fixed_length() and the read_sep_field()
functions.
Removed wrong setting of the table->auto_increment_field_not_null variable in
the read_sep_field() function.


mysql-test/t/loaddata.test:
  Added a test case for the bug#27586: Wrong autoinc value assigned by LOAD DATA in the
  NO_AUTO_VALUE_ON_ZERO mode.
mysql-test/r/loaddata.result:
  Added a test case for the bug#27586: Wrong autoinc value assigned by LOAD DATA in the
  NO_AUTO_VALUE_ON_ZERO mode.
sql/sql_load.cc:
  Bug#27586: Wrong autoinc value assigned by LOAD DATA in the
  NO_AUTO_VALUE_ON_ZERO mode.
  The table->auto_increment_field_not_null variable is reset now right after a
  row is being written in the read_fixed_length() and the read_sep_field()
  functions.
  Remove wrong setting of the table->auto_increment_field_not_null variable in
  the read_sep_field() function.