Double the time waiting post replication restart

[andyedison]

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Description

This PR increases the startSlavePostWaitMilliseconds as we are seeing an error when running gh-ost in some cloud environments that the Slave_IO_Running is Connecting rather than Yes as expected.

We found this old PR that described the issue we're having https://github.com/github/gh-ost/pull/337 - as a first step we are increasing by doubling the value. If this test is successful, then we'll look into making this something that could be configured.

In case this PR introduced Go code changes:

• [ ] contributed code is using same conventions as original code
• [ ] script/cibuild returns with no formatting errors, build errors or unit test errors.

[andyedison]

Targeted the wrong branch > will use https://github.com/github/gh-ost/pull/1422