Use updated dl_type when checking actions that use fields

Use updated dl_type when checking actions that use fields

Update handling of the following actions to use the dl_type set by MPLS
push and pop actions if it differs from the original dl_type. This is
consistent with the existing checking of load actions and allows
their existing checks to enforce dl_type pre-requisites correctly.

	output_reg
	bundle
	reg_move
	stack_push
	stack_pop
	learn
	multipath

In order to avoid the verbosity of updating the flow for each applicable
action the update is treated as a common case and performed in
ofpact_check().  This was suggested by Jesse Gross.

Cc: Jesse Gross <jesse@nicira.com>
Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Jesse Gross <jesse@nicira.com>