BUG/MEDIUM: lb-chash: Fix the realloc() when the number of nodes is increased

BUG/MEDIUM: lb-chash: Fix the realloc() when the number of nodes is increased

When the number of nodes is increased because the server weight is changed, the
nodes array must be realloc. But its new size is not correctly set. Only the
total number of nodes is used to set the new size. But it must also depends on
the size of a node. It must be the total nomber of nodes times the size of a
node.

This issue was reported on Github (#189).

This patch must be backported to all versions since the 1.6.