fix potential memory leak in unbound-host when errors happen

fix potential memory leak in unbound-host when errors happen

==3709953== HEAP SUMMARY:
==3709953==     in use at exit: 276,541 bytes in 23 blocks
==3709953==   total heap usage: 29 allocs, 6 frees, 280,682 bytes allocated
==3709953==
==3709953== 1 bytes in 1 blocks are still reachable in loss record 1 of 23
==3709953==    at 0x4866EC0: malloc (in /usr/lib64/valgrind/vgpreload_memcheck-arm64-linux.so)
==3709953==    by 0x48E2BC3: ub_initstate (random.c:85)
==3709953==    by 0x489B067: ub_ctx_create_nopipe (libunbound.c:114)
==3709953==    by 0x489B31F: ub_ctx_create (libunbound.c:180)
==3709953==    by 0x10E203: main (unbound-host.c:433)
==3709953==
......
==3709953== 8,192 bytes in 1 blocks are still reachable in loss record 22 of 23
==3709953==    at 0x4866EC0: malloc (in /usr/lib64/valgrind/vgpreload_memcheck-arm64-linux.so)
==3709953==    by 0x48E427B: regional_create_custom (regional.c:94)
==3709953==    by 0x48DEA03: edns_strings_create (edns.c:57)
==3709953==    by 0x489B0F3: ub_ctx_create_nopipe (libunbound.c:157)
==3709953==    by 0x489B31F: ub_ctx_create (libunbound.c:180)
==3709953==    by 0x10E203: main (unbound-host.c:433)
==3709953==
==3709953== 262,144 bytes in 1 blocks are still reachable in loss record 23 of 23
==3709953==    at 0x486933C: calloc (in /usr/lib64/valgrind/vgpreload_memcheck-arm64-linux.so)
==3709953==    by 0x48C826F: config_create (config_file.c:179)
==3709953==    by 0x48C85AF: config_create_forlib (config_file.c:383)
==3709953==    by 0x489B0BB: ub_ctx_create_nopipe (libunbound.c:130)
==3709953==    by 0x489B31F: ub_ctx_create (libunbound.c:180)
==3709953==    by 0x10E203: main (unbound-host.c:433)
==3709953==
==3709953== LEAK SUMMARY:
==3709953==    definitely lost: 0 bytes in 0 blocks
==3709953==    indirectly lost: 0 bytes in 0 blocks
==3709953==      possibly lost: 0 bytes in 0 blocks
==3709953==    still reachable: 276,541 bytes in 23 blocks
==3709953==         suppressed: 0 bytes in 0 blocks
==3709953==
==3709953== For lists of detected and suppressed errors, rerun with: -s
==3709953== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

Signed-off-by: eaglegai <eaglegai@163.com>