b=20278 ASSERTION(cli->cl_avail_grant >= 0) failed

b=20278 ASSERTION(cli->cl_avail_grant >= 0) failed

i=tom.wang
i=robert.read

This patch tries to address several issues:
- osc_init_grant(): calculate avail_grant according to recovery status.
- osc_reconnect(): request grant should include cl_dirty.
- filter_grant(): beside server reboot, we should also grant the requested
  amount in case of normal reconnect.
- round-up grant amount instead of round-down, otherwise client would still
  have situation that dirty > granted.