mxmirror: stricter assembly regexes

After some discussion, the name of assemblies is
a capital letter followed by four digits, where the
first digit resembles the single disk size in Gb.
A 10Gb disk will get an 'a', so we can steal away with
hex-digits at the first place.

Thus /[XCMD][\da-f]\d\d\d/ should be used at every place,
where assemblies are handled.

mxmirror/mxmirror

@@ -646,7 +646,7 @@ sub convert_to_sourcepath {
 
     my ($jbod, $path, $host, $hostpath, $partition);
 
-    if(($jbod, $path) = $string =~ /^([XCMD]\d+)(.*?)$/) {
+    if(($jbod, $path) = $string =~ /^([XCMD][\da-f]\d\d\d)(.*?)$/) {
         unless(defined $jbodmap->{$jbod}) {
            printf STDERR "**ERROR: unknown jbod: $string";
            next;
@@ -712,7 +712,7 @@ sub convert_to_destinationpath {
 
     my ($jbod, $path, $host, $hostpath, $partition);
 
-    if(($jbod, $path) = $string =~ /^([XCMD]\d+)(.*?)$/) {
+    if(($jbod, $path) = $string =~ /^([XCMD][\da-f]\d\d\d)(.*?)$/) {
         unless(defined $jbodmap->{$jbod}) {
            printf STDERR "**ERROR: unknown jbod: $string";
            next;
@@ -882,7 +882,7 @@ sub read_jbodmap {
     my $map = {};
 
     foreach(<F>) {
-        next unless (m(/amd/(.*?)/[XCMD]/([XCMD]\d+)));
+        next unless (m(/amd/(.*?)/[XCMD]/([XCMD][\da-f]\d\d\d)));
         $map->{$2} = $1;
     }