Rank deficiency issue

```julia
linear13: Test Failed at /home/blegat/.julia/dev/MathOptInterface/src/Test/contlinear.jl:1317
Expression: ≈(MOI.get(model, MOI.ConstraintPrimal(), c2), 0, atol=atol, rtol=rtol)
Evaluated: 1.7999998823840366 ≈ 0 (atol=0.0001, rtol=0.0001)
Stacktrace:
[1] linear13test(::MathOptInterface.Bridges.SingleBridgeOptimizer{MathOptInterface.Bridges.SplitIntervalBridge{Float64,F} where F<:MathOptInterface.AbstractScalarFunction,MathOptInterface.Bridges.SplitIntervalInstance{Float64},MathOptInterface.Utilities.CachingOptimizer{SeDuMi.Optimizer,ModelData{Float64}}}, ::MathOptInterface.Test.TestConfig) at /home/blegat/.julia/dev/MathOptInterface/src/Test/contlinear.jl:1317
[2] macro expansion at /home/blegat/.julia/dev/MathOptInterface/src/Test/config.jl:51 [inlined]
[3] macro expansion at /build/julia/src/julia-1.0.3/usr/share/julia/stdlib/v1.0/Test/src/Test.jl:1083 [inlined]
[4] contlineartest(::MathOptInterface.Bridges.SingleBridgeOptimizer{MathOptInterface.Bridges.SplitIntervalBridge{Float64,F} where F<:MathOptInterface.AbstractScalarFunction,MathOptInterface.Bridges.SplitIntervalInstance{Float64},MathOptInterface.Utilities.CachingOptimizer{SeDuMi.Optimizer,ModelData{Float64}}}, ::MathOptInterface.Test.TestConfig, ::Array{String,1}) at /home/blegat/.julia/dev/MathOptInterface/src/Test/config.jl:51
>> Warning: Rank deficient, rank = 1, tol = 4.615110e-14.
> In sedumi (line 268)

>> Warning: Rank deficient, rank = 1, tol = 4.615110e-14.
> In sedumi (line 268)
```