Cleanup lldb-mi test cases.
Following changes were done.
1. Remove the extra line after -exec-run.
2. Remove check for prompt.
3. Remove 'quit' command. 

Initial patch was contributed by ki.stfu@gmail.com.



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@224990 91177308-0d34-0410-b5e6-96231b3b80d8