type inference fix

Not sure why this is needed, but this fixes an error:
```
ERROR: `putvarboundslice` has no method matching putvarboundslice(::MSKtask, ::Int64, ::Int64, ::Array{Any,1}, ::Array{Float64,1}, ::Array{Float64,1})
 in loadconicproblem! at /home/mlubin/.julia/v0.3/Mosek/src/MosekConicInterface.jl:424
```