[SPARK-4832][Deploy]some other processes might take the daemon pid

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