Wrong return type for reductions of complex CuArrays

[Sleort]

Describe the bug
With ordinary Arrays, we have

x = rand(ComplexF32, 1)
sum(abs, x) isa Float32 # true
prod(abs, x) isa Float32 # true

as expected, while for CuArrays

using CuArrays
y = cu(x)
sum(abs, y) isa Float32 # false -- sum(abs, y) turns out to be a ComplexF32 with zero imaginary part
prod(abs, y) isa Float32 # false

The same happens to be the case when replacing abs with abs2 or ComplexF32 with ComplexF64.

Expected behavior
CuArrays should behave the same way as Arrays, i.e.

sum(abs, y) isa Float32 # true -- NOT a ComplexF32
prod(abs, y) isa Float32 # true

Environment details
Details on Julia:

julia> versioninfo()
Julia Version 1.3.1
Commit 2d5741174c (2019-12-30 21:36 UTC)
Platform Info:
  OS: Linux (x86_64-pc-linux-gnu)
  CPU: Intel(R) Core(TM) i7-8750H CPU @ 2.20GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-6.0.1 (ORCJIT, skylake)

Julia packages:

(v1.3) pkg> st CuArrays
    Status `~/.julia/environments/v1.3/Project.toml`
  [79e6a3ab] Adapt v1.0.0
  [fa961155] CEnum v0.2.0
  [3895d2a7] CUDAapi v2.1.0
  [c5f51814] CUDAdrv v5.0.1
  [be33ccc6] CUDAnative v2.7.0
  [3a865a2d] CuArrays v1.6.0
  [864edb3b] DataStructures v0.17.7
  [872c559c] NNlib v0.6.2

CUDA: toolkit and driver version

nvcc: NVIDIA (R) Cuda compiler driver
Copyright (c) 2005-2019 NVIDIA Corporation
Built on Fri_Feb__8_19:08:17_PST_2019
Cuda compilation tools, release 10.1, V10.1.105