elf: Call free from base namespace on error in dl-libc.c [BZ #27646]

In dlerror_run, free corresponds to the local malloc in the
namespace, but GLRO (dl_catch_error) uses the malloc from the base
namespace.  elf/tst-dlmopen-gethostbyname triggers this mismatch,
but it does not crash, presumably because of a fastbin deallocation.

Fixes commit c2059edc ("elf: Use
_dl_catch_error from base namespace in dl-libc.c [BZ #27646]") and
commit b2964eb1 ("dlfcn: Failures
after dlmopen should not terminate process [BZ #24772]").