Fix cross-testing of tst-ifunc-fault-* tests.

The tests elf/tst-ifunc-fault-bindnow and elf/tst-ifunc-fault-lazy
fail in cross-testing because they run the dynamic linker directly
without using the test wrapper.  This patch fixes them to use the test
wrapper instead.

Tested that this fixes the failure of those two tests for powerpc
soft-float.