check: fix extended names handling

check: fix extended names handling

The code handling "./check foo/123", when the real test is
"foo/123-bar-baz" was moved to the earliest position, so everything
working with the test name or path will know the full name. Thus, no
"123" and "123-bar-baz" mix is possible.

An example of this issue is $testname.notrun file. When _notrun
"foo" was run during ./check foo/$name command, it created
$name.notrun. But few lines later, it wanted $fullname.notrun. So if
you did ./check foo/999, but the file was 999-bar-baz, then you got
comparing outputs (and most likely a fail) instead of a skip.

Another example of this mix is in xfstests output:
./check xfs/999
[...]
xfs/999 0s ... 0s
Ran: xfs/999-test-case

Signed-off-by: Jan Tulak <jtulak@redhat.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>