ovsdb-server: Fix memory leak using perf counter without initialization.

perf_counter_accumulate() is invoked without perf_counters_init() being
called first, which leads to a memory leak reported by Valgrind (test
cases 104, 106, and 107). A call trace is below:
    xmalloc (util.c:112)
    shash_add_nocopy__ (shash.c:109)
    shash_add_nocopy (shash.c:121)
    shash_add (shash.c:129)
    shash_add_once (shash.c:136)
    shash_add_assert (shash.c:146)
    perf_counter_init (perf-counter.c:86)
    perf_counter_accumulate (perf-counter.c:95)
    ovsdb_txn_commit (transaction.c:850)
    ovsdb_file_open__ (file.c:217)
    open_db (ovsdb-server.c:418)
    main (ovsdb-server.c:263)

Signed-off-by: William Tu <[email protected]>
Signed-off-by: Daniele Di Proietto <[email protected]>
Co-authored-by: Daniele Di Proietto <[email protected]>
Signed-off-by: Ben Pfaff <[email protected]>

AUTHORS

@@ -215,6 +215,7 @@ Wei Li                  [email protected]
 Wei Yongjun             [email protected]
 Wenyu Zhang             [email protected]
 William Fulton
+William Tu              [email protected]
 YAMAMOTO Takashi        [email protected]
 Yasuhito Takamiya       [email protected]
 yinpeijun               [email protected]

ovsdb/ovsdb-server.c

@@ -259,6 +259,9 @@ main(int argc, char *argv[])
     shash_init(&all_dbs);
     server_config.all_dbs = &all_dbs;
     server_config.jsonrpc = jsonrpc;
+
+    perf_counters_init();
+
     SSET_FOR_EACH (db_filename, &db_filenames) {
         error = open_db(&server_config, db_filename);
         if (error) {
@@ -297,8 +300,6 @@ main(int argc, char *argv[])
 
     daemonize_complete();
 
-    perf_counters_init();
-
     if (!run_command) {
         /* ovsdb-server is usually a long-running process, in which case it
          * makes plenty of sense to log the version, but --run makes