logging: Remove multiple definitions of DEFAULT_LOG_FILE_DIRECTORY

Change-Id: I8d670a228d3c1282aa7d70b151f166d04abc40e5
BUG: 764890
Signed-off-by: Vijay Bellur <vbellur@redhat.com>
Reviewed-on: http://review.gluster.org/5909
Reviewed-by: Anand Avati <avati@redhat.com>
Tested-by: Anand Avati <avati@redhat.com>