[test] Don't drop existing categories for methods.
[test] Don't drop existing categories for methods.

The change in r324488 dropped the existing category attribute in for
instance methods. This patch corrects that.

Differential revision: https://reviews.llvm.org/D43024

git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@324492 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lldb,llvm-mirror/lldb,llvm-mirror/lldb,apple/swift-lldb,llvm-mirror/lldb,apple/swift-lldb,apple/swift-lldb,llvm-mirror/lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb