Ticket History #3714: fix incorrect padata memory allocation in send_tgs.c

send_tgs.c accepts additional padata. If this is supplied to it then
there is an incorrect memory allocation

at line 230

for (counter = padata; *counter; counter++, i++);
combined_padata = (krb5_pa_data **)malloc(i+2);

should read

for (counter = padata; *counter; counter++, i++);
combined_padata = (krb5_pa_data **)malloc((i+2) *
sizeof(*combined_padata));