Update mysql createindex bug

(cherry picked from commit a7a73fd94b)

# Conflicts:
#	Src/Asp.Net/SqlSugar/Realization/MySql/DbMaintenance/MySqlDbMaintenance.cs

Src/Asp.NetCore2/SqlSugar/Abstract/DbMaintenanceProvider/Methods.cs

@@ -333,7 +333,8 @@ namespace SqlSugar
         }
         public virtual bool IsAnyIndex(string indexName)
         {
-            string sql = string.Format(this.IsAnyIndexSql, indexName);
+            //string sql = string.Format(this.IsAnyIndexSql, indexName);
+            string sql = string.Format(this.IsAnyIndexSql, indexName, this.Context.Ado.Connection.Database);
             return this.Context.Ado.GetInt(sql)>0;
         }
         public virtual bool AddRemark(EntityInfo entity)

Src/Asp.NetCore2/SqlSugar/Realization/MySql/DbMaintenance/MySqlDbMaintenance.cs

@@ -268,7 +268,7 @@ namespace SqlSugar
         {
             get
             {
-                return "SELECT count(*) FROM information_schema.statistics WHERE index_name = '{0}'";
+                return "SELECT count(*) FROM information_schema.statistics WHERE index_name = '{0}' and index_schema = '{1}'";
             }
         }
         #endregion