always set our rails root to our root

this works fine when calling any framework binaries
from their path as CWD. if you call tehm from another path
you will get an incorrect root which can cause certain things to load
incorrectly

Signed-off-by: David Maloney <DMaloney@rapid7.com>
Merge branch 'staging/electro-release' into bug/MSP-11050/rails_root
Merge pull request #3644 from dmaloney-r7/bug/MSP-11050/rails_root

MSP-11050 #land
Merge branch 'staging/electro-release' into aruba-testing