Try to fix SENTINEL SIMULATE-FAILURE test by re-source init-tests before each test (#12194)

This test was introduced in #12079, it works well most of the time, but
occasionally fails:
```
00:34:45> SENTINEL SIMULATE-FAILURE crash-after-election works: OK
00:34:45> SENTINEL SIMULATE-FAILURE crash-after-promotion works: FAILED: Sentinel set crash-after-promotion but did not exit
```

Don't know the reason, it may be affected by the exit of the previous
crash-after-election test. Because it doesn't really make much sense to
go deeper into it now, we re-source init-tests to get a clean environment
before each test, to try to fix this.

After applying this change, we found a new error:
```
16:39:33> SENTINEL SIMULATE-FAILURE crash-after-election works: FAILED: caught an error in the test couldn't open socket: connection refused
couldn't open socket: connection refused
```

I am guessing the sentinel triggers failover and exits before SENTINEL FAILOVER,
added a new || condition in wait_for_condition to fix it.