make sure we quote extra_kernel_options

argparse will remove quotations, breaking extra_kernel_options and
inspector_extra_kernel_options when more than one option is used, e.g.

  --extra-vars extra_kernel_options="console=tty1 console=ttyS0,115200n8"

Change-Id: I324e1681303115162656f39d7b6cd60a3e717b9f

bifrost/cli.py

@@ -50,9 +50,16 @@ def log(*message, only_if=True):
 
 def process_extra_vars(extra_vars):
     for item in extra_vars:
+
+        # argparse removes quotes, just add quotes for these vars
+        if 'extra_kernel_options=' in item:
+            key, value = item.split('=', 1)
+            item = key + '="' + value + '"'
+
         if item.startswith('@'):
             # Make sure relative paths still work
             item = '@' + os.path.abspath(item[1:])
+
         yield ('-e', item)