task/ansible: reset fail_log file index
task/ansible: reset fail_log file index

The yaml.safe_load reads the fail_log opened file
and shifts the offset to the end of stream.
However in case of error we need to shift offset
to the begin of the file stream, so we can read
data again.

Signed-off-by: Kyr Shatskyy <82d0c7561ff7e9a20a19db22e8fb5b2adaa3d71e@suse.com>

ceph/teuthology,dmick/teuthology,SUSE/teuthology,SUSE/teuthology,dmick/teuthology,ktdreyer/teuthology,ktdreyer/teuthology,dmick/teuthology,ceph/teuthology,SUSE/teuthology