[FIX] account: restore cross-account reconciliation check, disabled by mistake

Both the FY closing change and the removal of the
check occurred at revision 6529
6529 revid:qdp-launchpad@openerp.com-20120209170333-8xu7r21hencjwu73.

Also removed code specific to fiscal year closing
in the regular reconciliation operation, as the
FY closing is now using a dedication reconciliation
algorithm.