Fix unlikely leak in sendto_kdc

If a TCP connection is killed after it allocates the buffer (so is no
longer in READING state), free the buffer during cleanup.

(cherry picked from commit 6895dc9f204520e7f4da8da879cc67c149bc4e6b)

https://github.com/krb5/krb5/commit/c36c4e4b12ed10d2fe4c8c0293e036dff8985758
Author: Greg Hudson <ghudson@mit.edu>
Committer: Tom Yu <tlyu@mit.edu>
Commit: c36c4e4b12ed10d2fe4c8c0293e036dff8985758
Branch: krb5-1.13
 src/lib/krb5/os/sendto_kdc.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)