LU-3142 tests: use echoerr() to redirect debug logs

LU-3142 tests: use echoerr() to redirect debug logs

This patch fixes run_dd.sh to use echoerr() for redirecting
debug logs to the log file instead of messing up the output.

Test-Parameters: clientdistro=el6 serverdistro=el6 \
clientarch=x86_64 serverarch=x86_64 clientcount=4 \
osscount=2 mdscount=2 austeroptions=-R failover=true \
useiscsi=true testlist=recovery-double-scale

Signed-off-by: Jian Yu <jian.yu@intel.com>
Change-Id: I72c02a38c22fca4e7e806af6771e135efd506478
Reviewed-on: http://review.whamcloud.com/6027
Tested-by: Hudson
Reviewed-by: Li Wei <wei.g.li@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Tested-by: Hongchao Zhang <hongchao.zhang@intel.com>
Reviewed-by: Hongchao Zhang <hongchao.zhang@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>