plugin: add bank name to bank_info struct

Problem: the bank_info struct does not contain the name of the bank in
the struct, which can make it more tedious to find the name of the bank
because you have to look at the key of the map in order to find it. It
would be more convenient if the name was also in the struct.

Add the bank name to the struct attached with each user/bank
combination.

src/plugins/mf_priority.cpp

@@ -65,6 +65,7 @@ std::map<std::string, struct queue_info> queues;
 std::map<int, std::string> users_def_bank;
 
 struct bank_info {
+    std::string bank_name;
     double fairshare;
     int max_run_jobs;
     int cur_run_jobs;
@@ -524,6 +525,7 @@ static void rec_update_cb (flux_t *h,
         struct bank_info *b;
         b = &users[uid][bank];
 
+        b->bank_name = bank;
         b->fairshare = fshare;
         b->max_run_jobs = max_running_jobs;
         b->max_active_jobs = max_active_jobs;
@@ -755,6 +757,7 @@ static void add_missing_bank_info (flux_plugin_t *p, flux_t *h, int userid)
     b = &users[userid]["DNE"];
     users_def_bank[userid] = "DNE";
 
+    b->bank_name = "DNE";
     b->fairshare = 0.1;
     b->max_run_jobs = BANK_INFO_MISSING;
     b->cur_run_jobs = 0;