Fix Linux CI

[ReubenHill]

CI for #27 failed on linux but worked on local linux machines. (See report at https://travis-ci.org/Gowerlabs/LibFTD2XX.jl/builds/511412464)

Cause

Calling FT_CreateDeviceInfoList, which should return FT_OK::FT_STATUS_ENUM = 0 and populate a DWORD reference with the number of devices (0 on a virtual machine) instead returns FT_OTHER_ERROR::FT_STATUS_ENUM = 18.

Making first function call FT_GetDeviceInfoList instead gave the same return value.

The cause of these return values is unknown, but seems to be something specific to CI.

Report Snippet

ERROR: LoadError: FT_OTHER_ERROR::FT_STATUS_ENUM = 18
Stacktrace:
 [1] check at /home/travis/build/Gowerlabs/LibFTD2XX.jl/src/wrapper.jl:292 [inlined]
 [2] FT_CreateDeviceInfoList at /home/travis/build/Gowerlabs/LibFTD2XX.jl/src/wrapper.jl:315 [inlined]
 [3] createdeviceinfolist() at /home/travis/build/Gowerlabs/LibFTD2XX.jl/src/LibFTD2XX.jl:551
 [4] top-level scope at none:0
 [5] include at ./boot.jl:317 [inlined]
 [6] include_relative(::Module, ::String) at ./loading.jl:1044
 [7] include(::Module, ::String) at ./sysimg.jl:29
 [8] include(::String) at ./client.jl:392
 [9] top-level scope at none:0
in expression starting at /home/travis/build/Gowerlabs/LibFTD2XX.jl/test/runtests.jl:11
ERROR: Package LibFTD2XX errored during testing
Stacktrace:
 [1] pkgerror(::String, ::Vararg{String,N} where N) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Pkg/src/Types.jl:120
 [2] #test#65(::Bool, ::Function, ::Pkg.Types.Context, ::Array{Pkg.Types.PackageSpec,1}) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Pkg/src/Operations.jl:1357
 [3] #test at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Pkg/src/API.jl:0 [inlined]
 [4] #test#42(::Bool, ::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, ::Function, ::Pkg.Types.Context, ::Array{Pkg.Types.PackageSpec,1}) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Pkg/src/API.jl:273
 [5] #test at ./none:0 [inlined]
 [6] #test#41 at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Pkg/src/API.jl:255 [inlined]
 [7] #test at ./none:0 [inlined]
 [8] #test#40 at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Pkg/src/API.jl:254 [inlined]
 [9] #test at ./none:0 [inlined]
 [10] #test#39 at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Pkg/src/API.jl:253 [inlined]
 [11] (::getfield(Pkg.API, Symbol("#kw##test")))(::NamedTuple{(:coverage,),Tuple{Bool}}, ::typeof(Pkg.API.test), ::String) at ./none:0
 [12] top-level scope at none:0

[samuelpowell]

CI enabled but with allowed failures in #45