hash-map-tests.c: fix memory leak

hash-map-tests.c: fix memory leak

This commit makes "make selftest-valgrind" clean by fixing this leak:

4 bytes in 1 blocks are definitely lost in loss record 1 of 734
   at 0x483AB1A: calloc (vg_replace_malloc.c:762)
   by 0x261DBE0: xcalloc (xmalloc.c:162)
   by 0x2538C46: selftest::test_map_of_strings_to_int() (hash-map-tests.c:87)
   by 0x253ABD2: selftest::hash_map_tests_c_tests() (hash-map-tests.c:307)
   by 0x24A885B: selftest::run_tests() (selftest-run-tests.c:65)
   by 0x1373D80: toplev::run_self_tests() (toplev.c:2339)
   by 0x1373FA7: toplev::main(int, char**) (toplev.c:2421)
   by 0x2550EFF: main (main.c:39)

gcc/ChangeLog:
	* hash-map-tests.c (selftest::test_map_of_strings_to_int): Fix
	memory leak.

From-SVN: r280015