"make check" without a previous "make" failed, because

checkkomspace was not built early enough.  Also, the test suite
should not fail on platforms that don't support fsusage.c.
* src/server/Makefile.am (CHECKKOMSPACE): New empty variable.
Append checkkomspace$(EXEEXT) to it if we HAVE_FSUSAGE.
(check-lyskomd): Depend on $(CHECKKOMSPACE).
(check-recursive): Ditto.
* src/server/testsuite/lyskomd.0/50.exp: Report "unsupported" if
checkkomspace is not built.  (Don't fail with fatal errors.)