libsnapshot: Pass MSG_NOSIGNAL socket flags

If one end of the communication socket is closed for some reason, there
is no need to terminate the daemon or the client. Mask
the SIGPIPE using MSG_NOSIGNAL flag - we will
still get EPIPE error but process will not be terminated.

Bug: 186213024
Test: Full OTA
Signed-off-by: Akilesh Kailash <akailash@google.com>
Change-Id: Iaa53545c0c4059618f6b49afb9ec24ea5372c7e0