test_dictionary: fix warning/error when compiling with -O1 or higher
test_dictionary: fix warning/error when compiling with -O1 or higher

If test suite is built with -01 or higher, and combined with -Wall,
it produces the following error:

test_dictionary.c: In function ‘get_dump’:
test_dictionary.c:131:10: warning: ignoring return value of ‘fread’, declared with attribute warn_unused_result [-Wunused-result]
     fread(dump_buff, 1, dump_size, fd);
          ^

The workaround is to assign return value to dump_size. The value returned by
fread() should be equal to original dump_size, unless an error occured. As
dump_size is not used after that call, it matters not whether check for error
is performed or not, thus it is skipped.

a2o/iniparser,a2o/iniparser,a2o/iniparser,a2o/iniparser