Log diagnostic when setting software breakpoints only on failure.
Log diagnostic when setting software breakpoints only on failure.

Previously we would be posting a "FAILED" message to the log channel even when
the operation succeeded.

Also, take this opportunity to add braces thus eliminating an "ambiguous else"
compiler warning.



git-svn-id: b33bab8abb5b18c12ee100cd7761ab452d00b2b0@123306 91177308-0d34-0410-b5e6-96231b3b80d8

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