replicate: set read-child to the subvolume which replied first (fastest)
replicate: set read-child to the subvolume which replied first (fastest)

In the old logic read-child was set to the last subvolume which replied.
Now it is updated to the first subvolume. This way we can ensure that local
servers are preferred for reads _most_ of the times.

Signed-off-by: Anand Avati <avati@gluster.com>
Signed-off-by: Anand V. Avati <avati@dev.gluster.com>

BUG: 1172 (ls -lh on NFS mount of 2-mirror replicate gives incorrect file size)
URL: http://bugs.gluster.com/cgi-bin/bugzilla3/show_bug.cgi?id=1172

Kaushikbv/Gluster,Kaushikbv/Gluster,Kaushikbv/Gluster