QmlCpp Debugging: Only set C++ breakpoints after QML is connected

QmlCpp Debugging: Only set C++ breakpoints after QML is connected

If one hits a C++ breakpoint before the QmlEngine is properly set up
the debugging actions are all disabled. Patch 58faedc4e tried to
fix this by automatically executing continue in these cases, but
this let to errors on Mac OS X. Instead just delay the setting of
C++ breakpoints.

Task-number: QTCREATORBUG-5681
Change-Id: I149dea9b453ed7abd33a1a93b5b546d7c6cda8fd
Reviewed-on: http://codereview.qt.nokia.com/2568
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Christiaan Janssen <christiaan.janssen@nokia.com>