When a process receives a fatal signal, it connects to debuggerd
and initiates a conversation over a socket. When the crashing
process is debuggerd, the conversation stalls forever, and you
stop getting native crash details.
This resets the signal handlers to SIG_DFL, so that debuggerd
simply crashes and gets restarted.
Bug 5035703
Change-Id: Ie081d710d046f701bca7e7d8ea3e1d24766d9f61