env.sh: fix reading address from file
env.sh: fix reading address from file

The address from `/.dbus/session-bus/...` contains extra quotes, be sure
to ignore that when looking for a match. Applies at least to Ubuntu
18.04.1 and Arch Linux:

    DBUS_SESSION_BUS_ADDRESS='unix:abstract=/tmp/dbus-PwqhKSpHLU,guid=4da07e8716d2862711608ba95baa254f'

Lekensteyn/netns