<rdar://problem/13831149>
<rdar://problem/13831149>

Recursive commands invocations are not currently supported by our CommandInterpreter
CommandScriptImport can actually be made to invoke itself recursively, so we need to work around that by clearing the m_exe_ctx
This is a short-term workaround, a more interesting solution would be to actually make sure recursive command invocations work properly

git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@181537 91177308-0d34-0410-b5e6-96231b3b80d8

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