Fix -break-insert without -f to cause an error if BP not resolved (MI)

For example:
was:
```
$ bin/lldb-mi ~/p/hello
[...]
-break-insert main
^done,bkpt={number="1",type="breakpoint",disp="keep",enabled="y",addr="0x0000000100000e2d",func="main",file="hello.cpp",fullname="/Users/Ilia
hello.cpp",line="14",pending=["main"],times="0",original-location="main"}
```

now:
```
$ bin/lldb-mi ~/p/hello
[...]
-break-insert main
^error,msg="Command 'break-insert'. Breakpoint location 'main' not found"
```

llvm-svn: 236832