Remove sed and move size check

There was a question on if the comment removals in the `sed` were
required. The comments (`#`) are created by vmdk-stream-converter and
seem to cause no issues. `ddb.comment` is no longer being written by the
tool anymore. Moved the check earlier to ensure the new header isn't too
large before running truncate (otherwise it may be too long, and we
remove bits we want)

live-build/functions

@@ -243,50 +243,33 @@ modify_vmdk_header() {
     # trim null bytes to treat as standard text file
     tr -d '\000' < $descriptor > $newdescriptor
 
-    # The sed lines below is where the magic is. Specifically:
-    #   ddb.toolsVersion: sets the open-vm-tools so that VMware shows
-    #       the tooling as current
-    #   ddb.virtualHWVersion: set the version to 7, which covers most
-    #       current versions of VMware
-    #   createType: make sure its set to stream Optimized
-    #   remove the vmdk-stream-converter comment and replace with
-    #       # Disk DescriptorFile. This is needed for Virtualbox
-    #   remove the comments from vmdk-stream-converter which causes
-    #       VirtualBox and others to fail VMDK validation
-
-    sed -i -e 's|# Description file.*|# Disk DescriptorFile|' \
-           -e '/# Believe this is random*/d' \
-           -e '/# Indicates no parent/d' \
-           -e '/# The Disk Data Base/d' \
-           -e '/ddb.comment*/d' \
-        $newdescriptor
-    
-    # grep for removal of the ddb.comment line to ensure removal
-    if grep -q "ddb.comment" $newdescriptor; then
-        echo "ddb.comment exists and will cause Virtualbox failures"; exit 1
-    fi
-
     # add newline to newdescriptor
     echo "" >> $newdescriptor
 
-    # add tools version
+    # add required tools version
     echo -n 'ddb.toolsVersion = "2147483647"' >> $newdescriptor
 
     # check ddb.toolsVersion in descriptor, otherwise image will fail
-    grep -q 'ddb.toolsVersion' $newdescriptor || {
-        echo 'failed to write version. Descriptor invalid'; exit 1;
-    }
+    if ! grep -q 'ddb.toolsVersion' $newdescriptor; then 
+        echo 'failed to write version. Descriptor invalid'; \
+        exit 1
+    fi
 
     # diff original descriptor and new descriptor for debugging
+    # diff exits 1 if difference. pipefail not set so piping diff
+    # to cat prints diff and swallows exit 1
     diff --text $descriptor $newdescriptor | cat
 
+
+    # The header must be 1024 or less before padding
+    if ! expr $(stat --format=%s ${newdescriptor}) \< 1025 > /dev/null 2>&1; then
+        echo "descriptor is too large, VMDK will be invalid!"; 
+        exit 1
+    fi
+
     # reset newdescriptor to be 1024
     truncate --no-create --size=1K $newdescriptor
 
-    # The header must be 1024 or less
-    expr $(stat --format=%s ${newdescriptor}) \< 1025 > /dev/null 2>&1 || {
-        echo "descriptor is too large, VMDK will be invalid!"; exit 1; }
-
     # Overwrite the vmdk header with our new, modified one
     dd conv=notrunc,nocreat \
         if="${newdescriptor}" of="${vmdk_name}" \