dm raid: cleanup parameter handling

Re-order the parameters so they are handled consistently in the same order
where defined, parsed and output.

Only include rebuild parameters in the STATUSTYPE_TABLE output if they were
supplied in the original table line.

Correct the parameter count when outputting rebuild: there are two words,
not one.

Use case-independent checks for keywords (as in other device-mapper targets).

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>