Don't throw in cholesky if check=false

[jishnub]

Fix JuliaLinearAlgebra/ArrayLayouts.jl#100

This mirrors the behavior in LinearAlgebra, and after this, the following are consistent:

julia> B = BandedMatrix(-3=> 2ones(2), -1=>ones(4), 0=>2ones(5)); Buplo = :L; SB = Symmetric(B, Buplo);

julia> cholesky(Matrix(SB), check = false)
Failed factorization of type Cholesky{Float64, Matrix{Float64}}

julia> cholesky(SB, check = false)
Failed factorization of type Cholesky{Float64, BandedMatrix{Float64, Matrix{Float64}, Base.OneTo{Int64}}}

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (7f123af) 89.43% compared to head (3e41c33) 89.43%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #389   +/-   ##
=======================================
  Coverage   89.43%   89.43%           
=======================================
  Files          25       25           
  Lines        3510     3510           
=======================================
  Hits         3139     3139           
  Misses        371      371           

Files Changed	Coverage Δ
src/lapack.jl	89.09% <100.00%> (ø)

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