busybox-initramfs/scripts/init: tweak default nfs mount options

- do soft instead of hard nfs mounts
- decrease timeo,retrans

default timeo (70) * our retrans (10) is a bit too high, causing
long lock-ups on resume from suspend with /storage on nfs (due to a
non-related connman bug)

I have a very basic nfs knowledge, but IMO if 2 retrans with 3 sec
timeout fails, there is a general networking problem and the nfs
share is "broken" anyway (loosy network or so)

ref #2596