MB-100 Normalize main vm process name in stats.

So that there's no need to do many lookups with different names. And
also given that we are going to have another vm for views and xdcr,
this will help differentiate them.

Change-Id: I7b4d49653c713ba1b47743166952e91b4f56aa74
Reviewed-on: http://review.couchbase.org/28931
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Artem Stemkovski <artem@couchbase.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
MB-100 Don't break badly when erlang:memory does not work.

erlang:memory stops working when any of alloc_util allocators are
disabled. And we want to give us an option of suggesting disabling
them to some customers.

Change-Id: I31cf673fcd1c46ae9e5701a30f93ac45ead783a6
Reviewed-on: http://review.couchbase.org/28932
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Artem Stemkovski <artem@couchbase.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>