redfishpower: make network error messages clearer

Problem: Redfishpower decided to output a generic "network error"
message when either a connection error occurred (i.e. typically
if the host is down) vs a operation timeout (i.e. such as a failed
DNS lookup).  It would be useful to know which one actually happened.

Split the "network error" message into two specific error messages.

src/redfishpower/redfishpower.c

@@ -1589,9 +1589,10 @@ static void shell(CURLM *mh)
                         err_exit(false, "private data not set in easy handle");
 
                     if (cmsg->data.result != 0) {
-                        if (cmsg->data.result == CURLE_COULDNT_CONNECT
-                            || cmsg->data.result == CURLE_OPERATION_TIMEDOUT)
-                            printf("%s: %s\n", pm->plugname, "network error");
+                        if (cmsg->data.result == CURLE_COULDNT_CONNECT)
+                            printf("%s: %s\n", pm->plugname, "couldn't connect");
+                        else if (cmsg->data.result == CURLE_OPERATION_TIMEDOUT)
+                            printf("%s: %s\n", pm->plugname, "operation timedout");
                         else if (cmsg->data.result == CURLE_HTTP_RETURNED_ERROR) {
                             /* N.B. curl returns this error code for all response
                              * codes >= 400.  So gotta dig in more.