LU-5312 fld: retry fld rpc until the import is closed

LU-5312 fld: retry fld rpc until the import is closed

Since LWP is not replayable, it should retry RPC until
the import is closed, otherwise it would cause unnecessary
failure of the application.

Change-Id: I66d52fefe472ff2b139aa74f837e32a1403c3b2a
Signed-off-by: Wang Di <di.wang@intel.com>
Reviewed-on: http://review.whamcloud.com/11039
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>