Cut down on object allocation in CipherInputStream

While installing large encrypted app, GC used to collect large
number of objects because when the data was being read from the input
stream, it used to place the same on a new byte array leaving the last
allocated array unused.

The same behavior was not observed on Android N maybe due to changes in
GC, however, it was creating the objects in a similar way it used to
create  in older versions.

This increases speed of CipherInputStreamBenchmark from 54ms to 28 ms.

Test: libcore.javax.crypto.CipherInputStreamTest
Test: org.apache.harmony.crypto.tests.javax.crypto.CipherInputStreamTest
Test: org.apache.harmony.crypto.tests.javax.crypto.CipherInputStream1Test

Bug: 6478569
Change-Id: I0cf0dc37e6513c08abcf2f3077db3dc9e6395b62