Fix confusing "resuming interrupted unknown" message

Dmitry reported seeing the following:

    $ sleep 2 & sleep 1; ./strace -erestart_syscall -p $!
    [1] 12345
    Process 12345 attached
    restart_syscall(<... resuming interrupted unknown ...>) = 0

Fixing it by replacing "unknown" with "system call".

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
1 file changed