curl: Fix determinism issues in ptest package

NROFF can take different values depending on the filesystem layout of the
host system and this leaks onto the target ptest package through the
Makefiles. Since ptest doesn't use them, delete them to resovle that issue.

Also ensure the task can rerun even if it already deleted configurehelp.pm

[YOCTO #14863]

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>