Use `grep -E` instead of `egrep` as `egrep` now emits a warning.
```
t/opt_report_checkpoints.t: failed
--- t/opt_report_checkpoints.t
+++ t/opt_report_checkpoints.t.err
@@ -8,6 +8,7 @@
> fi
$ sysbench ${SBTEST_SCRIPTDIR}/oltp_read_write.lua --db-driver=mysql --mysql-dry-run --time=3 --events=0 --report-checkpoints=1,2 run | egrep '(Checkpoint report|SQL statistics)'
+ egrep: warning: egrep is obsolescent; using grep -E
[ 1s ] Checkpoint report:
SQL statistics:
[ 2s ] Checkpoint report:
```
```
$ echo | egrep 'abc'
egrep: warning: egrep is obsolescent; using grep -E
$ grep --version
grep (GNU grep) 3.8
Copyright (C) 2022 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Written by Mike Haertel and others; see
<https://git.sv.gnu.org/cgit/grep.git/tree/AUTHORS>.
```
1. Fix drivers.t so it passes when no DB drivers are available.
2. Make it possible for the test suite to detect if certain DB drivers
are available, so individual tests that require them can be skipped.
If a test did not support intermediate reports (i.e. --report-interval
or --report-checkpoints), there was a confusing (but benign) error at
the end of the test: "Terminating the reporting thread failed".
