ipsec: fix instance, and cli del for new ipsec interface

ipsec: fix instance, and cli del for new ipsec interface

- use user instance number in interface name

Restore the behavior of previous versions where the IPsec tunnel
interface name contained the value of the user-provided instance number.
For example, a command similar to

	create ipsec tunnel local-ip . . . instance 5

would result in the creation of interface "ipsec5".

- ipsec: delete tunnel protection when asked

The "ipsec tunnel protect" command will parse a "del" argument but does
not undo the tunnel protection, leaving the SAs hanging around with
reference counts that were incremented by a previous invocation of the
command. Allow the tunnel protection to be deleted and also update the
help text to indicate that deletion is an option.

- test: ipsec: add test for ipsec interface instance

Also cleanup (unconfig) after TestIpsecItf4 NULL algo test.

Type: fix
Fixes: dd4ccf2623b5 ("ipsec: Dedicated IPSec interface type")
Signed-off-by: Eric Kinzie <ekinzie@labn.net>
Signed-off-by: Christian Hopps <chopps@labn.net>
Change-Id: Idb59ceafa0633040344473c9942b6536e3d941ce