Work around replay cache creation race

If two processes try to initialize the same replay cache at the same
time, krb5_rc_io_creat can race between unlink and open, leading to a
KRB5_RC_IO_PERM error.  When this happens, make the losing process
retry so that it can continue.

This does not solve the replay cache creation race, nor is that the
only replay cache race issue.  It simply prevents the race from
causing a spurious failure.

ticket: 3498
target_version: 1.13
tags: pullup