Add mdadm.conf to initrd if needed (#895805)

Check to see if the system needs mdadm.conf to boot, and if so, add it
to the initramfs.

fedup/boot.py

@@ -55,3 +55,17 @@ def initramfs_append(initramfs, files):
         (out, err) = cpio.communicate(input=filelist)
         if cpio.returncode:
             raise CalledProcessError(cpio.returncode, cmd, err)
+
+def need_mdadmconf():
+    '''Does this system need /etc/mdadm.conf to boot?'''
+    # NOTE: there are probably systems that have mdadm.conf but don't require
+    # it to boot, but I don't know how you tell the difference, so...
+    try:
+        for line in open("/etc/mdadm.conf"):
+            line = line.strip()
+            if line and not line.startswith("#"):
+                # Hey there's actual *data* in here! WE MIGHT NEED THIS!!
+                return True
+    except IOError:
+        pass
+    return False

fedup/sysprep.py

@@ -141,6 +141,10 @@ def modify_bootloader(kernel, initrd):
     boot.add_entry(kernel, initrd, banner=_("System Upgrade"), kargs=args)
 
 def prep_boot(kernel, initrd):
+    # check for systems that need mdadm.conf
+    if boot.need_mdadmconf():
+        log.info("appending /etc/mdadm.conf to initrd")
+        boot.initramfs_append(initrd, "/etc/mdadm.conf")
     # set up the boot args
     modify_bootloader(kernel, initrd)