[lldb][test] Fix missing-braces warnings in unit tests

```
/home/worker/2.0.1/lldb-x86_64-debian/llvm-project/lldb/unittests/Utility/ChecksumTest.cpp:15:38: warning: suggest braces around initialization of subobject [-Wmissing-braces]
static llvm::MD5::MD5Result hash1 = {0, 1, 2,  3,  4,  5,  6,  7,
                                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
                                     {
```
And others.