manager: if we are reexecuting, do not invoke any fallbacks

manager: if we are reexecuting, do not invoke any fallbacks

For https://bugzilla.redhat.com/show_bug.cgi?id=1986176:
if we are trying to reexecute, and this fails for any reason, we shouldn't
try to execute /sbin/init or /bin/sh. It is better to just freeze.
If we freeze it is easier to diagnose what happened, but if we execute
one of the fallbacks, we don't really know what will happen. In particular
the new init might just return, causing the machine to shut down. Or we
may successfully spawn /bin/sh, which could leave the machine open.