tools: Fix engine-config description processing

The "description" field was being processed by calling "getString" which
would split the string by the delimiter character behind the scenes,
causing only the first string to return.

Now, the string will be rejoined using that delimiter character (padding
is added because the split string is trimmed).

Change-Id: Ieb6bf225b06d0ed8491e3c725daef7bd500b1ae1
Signed-off-by: Mike Kolesnik <mkolesni@redhat.com>