The test failed on MacOS:
```
*** [err]: EXPIRE precision is now the millisecond in tests/unit/expire.tcl
Expected 'somevalue {}' to equal or match '{} {}'
```
`set a [r get x]`, even though we tried 10 times, sometimes we
still get {}, this is a time-sensitive test.
In this PR, we add the following changes:
1. More attempts, change it from 10 to 30.
2. More tolerant, change the `after 900` to `after 800`.
In addition, we judging $a in advance and changing `after 1100`
to `after 300`, this will save us some times.
6ab2174d37