Prevent collision between KUnifiedPush DBus and KRunner DBus

These share the same D-Bus service name (org.kde.neochat) which comes
with a fun little addition: KRunner activation! While this is not a
problem while NeoChat is running - since it's already registered - this
becomes an issue while searching for NeoChat in something like the
Kickoff. The Kickoff (and consequently, KRunner) tries to activate the
NeoChat D-Bus service which runs our unified push parts.

This introduces a "FakeRunner" which watches closely for calls to the
KRunner interface while we're in unified push mode (or directly called
from D-Bus but not running) so it quits immediately.

(cherry picked from commit 35b08d08)