Fix nasa#823, avoid infinite loop in CDS registry find

The CFE_ES_FindCDSInRegistry function had an unusual loop control
structure with mixed types of signed and unsigned.

This has the possibility of being infinite if the MaxNumRegEntries
is zero due to the way the end condition is structured.

Simplify to be like other loops and use unsigned int control variable.

fsw/cfe-core/src/es/cfe_es_cds.c

@@ -637,13 +637,10 @@ int32 CFE_ES_UnlockCDSRegistry(void)
 int32 CFE_ES_FindCDSInRegistry(const char *CDSName)
 {
     int32 RegIndx = CFE_ES_CDS_NOT_FOUND;
-    int32 i = -1;
+    uint32 i = 0;
 
-    do
+    while ( (RegIndx == CFE_ES_CDS_NOT_FOUND) && (i < CFE_ES_Global.CDSVars.MaxNumRegEntries) )
     {
-        /* Point to next record in the CDS Registry */
-        i++;
-
         /* Check to see if the record is currently being used */
         if (CFE_ES_Global.CDSVars.Registry[i].Taken == true)
         {
@@ -654,7 +651,11 @@ int32 CFE_ES_FindCDSInRegistry(const char *CDSName)
                 RegIndx = i;
             }
         }
-    } while ( (RegIndx == CFE_ES_CDS_NOT_FOUND) && (i < (CFE_ES_Global.CDSVars.MaxNumRegEntries-1)) );
+
+        /* Point to next record in the CDS Registry */
+        i++;
+
+    };
 
     return RegIndx;
 }   /* End of CFE_ES_FindCDSInRegistry() */
@@ -670,7 +671,7 @@ int32 CFE_ES_FindCDSInRegistry(const char *CDSName)
 int32 CFE_ES_FindFreeCDSRegistryEntry(void)
 {
     int32 RegIndx = CFE_ES_CDS_NOT_FOUND;
-    int32 i = 0;
+    uint32 i = 0;
 
     while ( (RegIndx == CFE_ES_CDS_NOT_FOUND) && (i < CFE_ES_Global.CDSVars.MaxNumRegEntries) )
     {