Workaround QEMU GDB server issue. 

During testing I observed QEMU send "$T02thread:01;#04" upon connection,
before any command from LLDB.  This change from gclayton accepts (and
discards) a packet immediately after sending the initial ack, to flush
the GDB remote pipeline.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@197579 91177308-0d34-0410-b5e6-96231b3b80d8