Memory leaks in VirtualFluids_GPUTests

With activated sanitizers, some memory leaks are displayed when running VirtualFluids_GPUTests.

Example output:

==19942==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 400 byte(s) in 1 object(s) allocated from:
    #0 0x7fdce216b808 in __interceptor_malloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cc:144
    #1 0x7fdcdb0a8fa1  (/usr/lib/x86_64-linux-gnu/libasan.so.5.0.0+0x55cfa1)

Direct leak of 104 byte(s) in 1 object(s) allocated from:
    #0 0x7fdce216b808 in __interceptor_malloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cc:144
    #1 0x7fdcdb145c4f  (/usr/lib/x86_64-linux-gnu/libasan.so.5.0.0+0x5f9c4f)

FYI: Sanitizers where added to the machine file like this:

add_compile_options(-fsanitize=address)
add_link_options(-fsanitize=address)
add_compile_options(-fsanitize=undefined)
add_link_options(-fsanitize=undefined)