xfs/029: filter out "extended-header: cycle: 1" from output

xfs/029: filter out "extended-header: cycle: 1" from output

When I test this case(default lsunit 256k), this case will fail,
as below:
cycle: 1        version: 2              lsn: 1,0        tail_lsn: 1,0
length of Log Record: 258048    prev offset: -1         num ops: 1

...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
extended-header: cycle: 1
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...

It reports this info because xfs_logprint only read 32k header every time, so it
needs to read more times. We can filter this useless info.

common/log also has _filter_logprint function. only library function is
prefixed with "_", remove '_'.

Signed-off-by: Yang Xu <xuyang2018.jy@cn.fujitsu.com>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>