heal: Enable logging for glfsheal.

logs will be written to <log-dir>/glfsheal-<volname>.log

Moved some non-essential frequent logs to DEBUG.

BUG: 1039544
Change-Id: I2aceda6e3092f8c5052e7a4b8b5dec3cdeebd9a9
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/7481
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Ravishankar N <ravishankar@redhat.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>