socket: uevent: use SO_RCVBUF instead of SO_RCVBUFFORCE

The SO_RCVBUFFORCE option requires the caller of uevent_create_socket()
to have net_admin capabilities.

Set platform default rcv/snd buffer sizes to 256kb that will always be
overridden by the device/target. However, it will allow
ueventd / healthd to use the uevent_create_socket() API w/o requiring
the net_admin capability.

Note: All devices override the buffer sizes according to the technology
maximum to at least ~8MB. So, the init.rc change here is to make sure
platform code can work w/o any overrides.

Test: no SELinux failures for healthd with 'net_admin' removed.

Bug: https://b/32733887



Change-Id: Ida346468cd550ad07901bf3a78ad508939849906
Signed-off-by: Sandeep Patil <sspatil@google.com>