perl: Call loadConfFile() in doInit to avoid screwing sqlite journal mode.

If the database is opened through perl bindings (and even though nix.conf has
use-sqlite-wal set to false), the database is automatically converted into WAL
mode. This makes the next nix process to access the database convert it back to
"truncate". If the database is still open at the time in wal mode by the perl
program, this fails and crashes the nix doing the wal -> truncate conversion.
Doh
Revert "Scan /proc/<pid>/cmdline for GC roots"

This reverts commit 194e3374b89b8b2dec6296923877304bdb5c6ae2.
Checking the command line for GC roots means that

  $ nix-store --delete $path

will fail because $path is now a root because it's mentioned on the
command line.