[backend] fix nativeonly dispatch handling

We need to deep copy or BSCando::cando has no helpers defined anymore

src/backend/bs_dispatch

@@ -124,9 +124,15 @@ my $port = 5252;        #'RR'
 $port = $1 if $BSConfig::reposerver =~ /:(\d+)$/;
 
 # strip helpers from cando
-my %cando = %BSCando::cando;
-for my $hostarch (values %cando) {
-  s/:.*// for @{$hostarch || []};
+my %cando; # = %BSCando::cando;
+for my $hostarch (keys %BSCando::cando) {
+  $cando{$hostarch} = [];
+  for (@{$BSCando::cando{$hostarch} || []}) {
+    # do a deep copy, we need unmodified BSCando::cando also
+    my $targetarch = $_;
+    $targetarch =~ s/:.*//;
+    push ( @{$cando{$hostarch}}, $targetarch );
+  }
 }
 
 # 4h build will add .5 to the load
@@ -1357,7 +1363,7 @@ while (1) {
         # a helper is needed for personality change?
         my $helper;
         /^\Q$arch\E:(.*)$/ && ($helper = $1) for @{$BSCando::cando{$harch}};
-        if ($helper && $workerinfo{$idle} && $workerinfo{$idle}->{hardware} && $workerinfo{$idle}->{hardware}->{nativeonly}) {
+        if ($helper && $workerinfo{$idle} && $workerinfo{$idle}->{hardware} && defined($workerinfo{$idle}->{hardware}->{nativeonly})) {
            next; # worker is not supporting the needed personality change
         }
 	if ($constraints) {

src/backend/bs_worker

@@ -676,7 +676,7 @@ if (open(FILE, "<", "/proc/cpuinfo")) {
       $hw->{'cpu'}->{'flag'} = \@cpuflags;
     } elsif (/^CPU implementer\s*:\s0x43/) {
       # aarch64 special case: does not support armvXl instruction set
-      $hw->{'nativeonly'} = undef;
+      $hw->{'nativeonly'} = "true";
     } elsif (/^cpu\s*:\sPOWER8/) {
       # PowerPC kernel does not provide any flags, but we need to be able
       # to distinguish between power7 and 8 at least