Remove vestigial CHECK_FOR_INTERRUPTS call.

Remove vestigial CHECK_FOR_INTERRUPTS call.

Commit e710b65c inserted code in md5_crypt_verify to disable and later
re-enable interrupts, with a CHECK_FOR_INTERRUPTS call as part of the
second step, to process any interrupts that had been held off.  Commit
6647248e removed the interrupt disable/re-enable code, but left behind
the CHECK_FOR_INTERRUPTS, even though this is now an entirely random,
pointless place for one.  md5_crypt_verify doesn't run long enough to
need such a check, and if it did, this would still be the wrong place
to put one.