To ensure Perl invocations within tests call the same Perl binary used
for running the tests, as specified or auto-detected via `PERL` env
(autotools) or `PERL_EXECUTABLE` setting (cmake). Instead of the first
`perl` executable found in `PATH`.)
Cherry-picked from #14949Closes#15097
Also introduce 'notexists' for verifying that directory entries do not
exist after a test. Now an explicit supported feature instead of using
"funny" perl in postcheck.
Closes#15046
- QUIT is not an important FTP command
- curl only sends it "best effort", meaning it might not be sent
- it is a known "flaky" thing in test output because of this
Closes#14404
The threee tags `<name>`, `</name>` and `<command>` were frequently used
with a leading space that this removes. The reason this habbit is so
widespread in testcases is probably that they have been copy and pasted.
Hence, fixing them all now might curb this practice from now on.
Closes#12028
