LU-5964 tests: open a large number of files at once

LU-5964 tests: open a large number of files at once

Modify createmany to allow keeping files open after creation to test
the total number of files that can be open at one time.  Also add a
sanity.sh test for this functionality.

Fix handling of last "-seconds" argument, but deprecate positional
parameters in favor of proper named argument parsing, since that is
more flexible and sustainable in the long term.

Order the include files alphabetically to simplify coding.
Order the argument parsing to be alphabetical to simplify coding.

Use booleans for do_* flags, and don't treat multiple of the same
argument as an error, that doesn't really improve usability at all.

Rename the "-r" option to "-u", to better match "unlinkmany", but
allow both to be accepted for the time being.  Allow "-u" (or "-r")
to be used in isolation to only delete files created in a prior run.
Print stats properly if only "-u" is specified, instead of assuming
that files are always being created in the same pass as deletion.

Print only the short program name instead of all of argv[0].  This
will also simplify multiplexing "createmany" as "unlinkmany" by name
at a later time.

Test-Parameters: trivial testlist=sanityn
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: I0e8c1af65dcf0b25065f26731c694f4beaab75d7
Reviewed-on: https://review.whamcloud.com/12885
Tested-by: Jenkins
Reviewed-by: Patrick Farrell <paf@cray.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>