protocol/server: Change log message severity

Change-Id: Ia6aaf8a106c26fa7118c86fadb6805d2877bb6ee
BUG: 849630
Signed-off-by: Vijay Bellur <vbellur@redhat.com>
Reviewed-on: http://review.gluster.org/6610
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>