ToolChainManager: Demote previously auto-detected ToolChains to manual
ToolChainManager: Demote previously auto-detected ToolChains to manual

Demote previously auto-detected toolchains to manual detection if
the binary is still found but no longer auto-detected.

This should address the bug were toolchains stayed around after they
were deregistered with the sdktool (without de-installing the binaries).

Task-number: QTCREATORBUG-12751
Change-Id: Ifcc8de0691c0b0839b8bf887a2a934c41101febe
Reviewed-by: Daniel Teske <d8a411aec9a206efedb4d45b75fe8d13f1e2b628@theqtcompany.com>

xianian/qt-creator,xianian/qt-creator,xianian/qt-creator,xianian/qt-creator,xianian/qt-creator,xianian/qt-creator,xianian/qt-creator,xianian/qt-creator,xianian/qt-creator