Initialize the aes key and iv variables

Static analysis indicated that the variables
were not initialized.  Strictly speaking, they
do not have to be, since they are protected
by a boolean flag variable.  But to make
coverity happy, initialize them (note that
the init value of zero is not any more
correct than a random uninitialized value
for the cryptographic operations, should
those values ever be used).

In addition, the assignment operator did
not copy the iv (even though it copied the
flag variable).  This was a real bug.

Fixes coverty 1023902