Some other processes might use the pid saved in pid file. In that case we should ignore it and launch daemons.

JIRA is down for maintenance. I will file one once it return.

Author: WangTaoTheTonic <barneystinson@aliyun.com>
Author: WangTaoTheTonic <wangtao111@huawei.com>

Closes #3683 from WangTaoTheTonic/otherproc and squashes the following commits:

daa86a1 [WangTaoTheTonic] some bash style fix
8befee7 [WangTaoTheTonic] handle the mistake scenario
cf4ecc6 [WangTaoTheTonic] remove redundant condition
f36cfb4 [WangTaoTheTonic] some other processes might take the pid