cipher.final should not be required for streaming ciphers

[kreynolds]

I misfiled this in jruby so I'm refiling it here as a more appropriate place.

Environment

Provide at least:

• jruby 9.2.6.0 (2.5.3) 2019-02-11 15ba00b OpenJDK 64-Bit Server VM 11.0.2+9 on 11.0.2+9 +jit [darwin-x86_64]
• Darwin Kelleys-MBP.neo.rr.com 18.6.0 Darwin Kernel Version 18.6.0: Thu Apr 25 23:16:27 PDT 2019; root:xnu-4903.261.4~2/RELEASE_X86_64 x86_64

Expected Behavior

• OpenSSL::Cipher.new('aes-256-ctr') should not require cipher.final for streaming ciphers

Actual Behavior

• It requires cipher.final to get the trailing bytes

Sample script

require 'openssl'
require 'securerandom'

# String which will have 4 trailing bytes
string = 'a'.b*20

cipher = OpenSSL::Cipher.new('aes-256-ctr')
cipher.iv = SecureRandom.random_bytes(16)
cipher.key = SecureRandom.random_bytes(32)

# str should be 20 bytes long
puts cipher.update(string).size

# In MRI
# => 20
# In JRuby
# => 16