Use blocking lock when creating db2 KDB

Use blocking lock when creating db2 KDB

In 1.11 we switched from non-blocking to blocking locks in the DB2
module, but we missed one call to krb5_lock_file() in ctx_create_db().
This non-blocking lock can cause krb5_db_promote() to fail if the
database is locked when we try to promote the DB, in turn causing
kdb5_util load to fail.  Correct this call to make krb5_db_promote()
more robust.

(cherry picked from commit 1868916dbb60a64b92da217257b4ed021262afd3)

ticket: 8367
version_fixed: 1.13.4
tags: -pullup
status: resolved