afsdb lookup shouldn't leak memory on realname lookup

afsdb lookup shouldn't leak memory on realname lookup

when looking up the "real" cell name, avoid leaking memory. the strdup
is inside a loop and would leak memory for each host returned above one.

Change-Id: I36cc9bd27ddc831121f47046daaab11f752012fe
Reviewed-on: http://gerrit.openafs.org/1538
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>