v-for循环＜el-form-item＞时应用popover

element-ui使用v-for循环el-form-item，如果循环的每栏都有popover，v-for 渲染多个 popover,
那么使用指令v-popover指向 Popover 的索引ref的方式触发，popover会失效
解决：

    <el-form ref="form" :model="form" label-width="80px">
      <el-row>
        <el-col
          :span="24"
        >
          固定列
        </el-col>
      </el-row>
      <el-form-item label="config0" >
        <el-input v-model="form.config0"></el-input>
      </el-form-item>
      
      <el-row>
        <el-col
          :span="24"
        >
          循环列
        </el-col>
        <div v-for="(item, index) in form.list" :key="index">
          <el-form-item v-if="item.ishow" :label="item.label">
            <el-input v-model="item.content">
              <i slot="prefix" class="el-input__icon el-icon-s-tools"></i>
              <el-popover
                placement="top-start"
                trigger="hover"
                slot="suffix"
              >
                <div>
                  <div>Edit</div>
                  <div>Add</div>
                  <div>Delete</div>
                </div>
                <i slot="reference" class="el-input__icon el-icon-more"></i>
              </el-popover>
            </el-input>
          </el-form-item>
        </div>
      </el-row>
    </el-form>

	  // 数据
      form: {
        config0: 'test',
        list: [
          {
            label: 'config1',
            content: 'despeic',
            ishow: true
          },
          {
            label: 'config2',
            content: 'scapje',
            ishow: true
          },
          {
            label: 'config3',
            content: 'interstiewn', 
            ishow: true
          }
        ],
      },

效果：
popover可以正常使用