Fixes a scoping bug that leads to "sticky" weights (apache#8606)

* Due to scoping, the last user-provided weight seen will be applied to all subsequent hosts that lack a weight

* Added a constant to specify the default weight

* Resets the weight to default prior to parsing each parent's configuration to ensure defaults are used when no weight exists

(cherry picked from commit 4e6dc02)

Author: elsloo

proxy/ParentSelection.cc

@@ -446,7 +446,7 @@ ParentRecord::ProcessParents(char *val, bool isPrimary)
   int port            = 0;
   char *tmp = nullptr, *tmp2 = nullptr, *tmp3 = nullptr;
   const char *errPtr = nullptr;
-  float weight       = 1.0;
+  float weight       = DEFAULT_PARENT_WEIGHT;
 
   if (parents != nullptr && isPrimary == true) {
     return "Can not specify more than one set of parents";
@@ -470,6 +470,7 @@ ParentRecord::ProcessParents(char *val, bool isPrimary)
   // Loop through the set of parents specified
   //
   for (int i = 0; i < numTok; i++) {
+    weight  = DEFAULT_PARENT_WEIGHT; // reset weight to the default
     current = pTok[i];
 
     // Find the parent port

proxy/ParentSelection.h

@@ -43,6 +43,7 @@
 #include <vector>
 
 #define MAX_PARENTS 64
+#define DEFAULT_PARENT_WEIGHT 1.0
 
 struct RequestData;
 struct matcher_line;