Fix leak in capaths processing

In k5_client_realm_path(), free the list of strings returned by
rtree_capaths_vals().

(cherry picked from commit 08756ce56bddab79afa4ee24b80243d8f822559d)

https://github.com/krb5/krb5/commit/1cd322e9b6927a0eb2e102c4501eef0c94c4102f
Author: Greg Hudson <ghudson@mit.edu>
Committer: Tom Yu <tlyu@mit.edu>
Commit: 1cd322e9b6927a0eb2e102c4501eef0c94c4102f
Branch: krb5-1.14
 src/lib/krb5/krb/walk_rtree.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)