test_cpuid_helpers: Run feature string to string roundtrip test
test_cpuid_helpers: Run feature string to string roundtrip test

This test seems to have fallen out of the test suite at some
point.

Signed-off-by: Euan Harris <c3b6e83069c8e9e3af49a38fec6026be89559638@citrix.com>

jjd27/xen-api,euanh/xen-api,thomassa/xen-api,thomassa/xen-api,Frezzle/xen-api,euanh/xen-api,srowe/xen-api,euanh/xen-api,thomassa/xen-api,euanh/xen-api,srowe/xen-api,rafalmiel/xen-api,jjd27/xen-api,rafalmiel/xen-api,Frezzle/xen-api,jjd27/xen-api,jjd27/xen-api,Frezzle/xen-api,rafalmiel/xen-api,thomassa/xen-api,rafalmiel/xen-api,thomassa/xen-api,thomassa/xen-api,euanh/xen-api,jjd27/xen-api,Frezzle/xen-api,euanh/xen-api,srowe/xen-api,srowe/xen-api,jjd27/xen-api,rafalmiel/xen-api,rafalmiel/xen-api,Frezzle/xen-api,srowe/xen-api