Do not block SIGTERM in init's child processes

Previously, unless the process unblocks the signal by itself,
the signal was never delivered to the process. This caused at
least one CTS test failure.

Bug: 72453675
Test: 'kill -TERM app_pid' terminates the app process

Change-Id: I3977cac75e2673b52c5cf91d34d7a9c258c1a0e4