LU-7045 osd: enough credits for single indirect block write

LU-7045 osd: enough credits for single indirect block write

For single indirect block case, if the i_data[LDISKFS_IND_BLOCK]
block is not allocated, the osd_calc_bkmap_credits() should declare
additional three blocks for subsequent write operation; otherwise,
preserve another single block for that.

Test-Parameters: alwaysuploadlogs envdefinitions=SLOW=yes,ENABLE_QUOTA=yes,CONF_SANITY_EXCEPT=45 mdtfilesystemtype=ldiskfs mdsfilesystemtype=ldiskfs ostfilesystemtype=ldiskfs clientdistro=el7 ossdistro=el7 mdsdistro=el7 mdtcount=1 testlist=conf-sanity,conf-sanity,conf-sanity,conf-sanity,conf-sanity
Test-Parameters: alwaysuploadlogs envdefinitions=SLOW=yes,ENABLE_QUOTA=yes,CONF_SANITY_EXCEPT=45 mdtfilesystemtype=ldiskfs mdsfilesystemtype=ldiskfs ostfilesystemtype=ldiskfs clientdistro=el7 ossdistro=el7 mdsdistro=el7 mdscount=2 mdtcount=4 testlist=conf-sanity,conf-sanity,conf-sanity,conf-sanity,conf-sanity
Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: I76b50cef8df56b49dae7afe4d759a55599548479
Reviewed-on: http://review.whamcloud.com/16330
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Tested-by: Andreas Dilger <andreas.dilger@intel.com>