Testing Farm tests should be using make-installed scripting

[praiskup]

First, great progress with the testing 🎉 !

I'm here to refer to this code:

postgresql-setup/tmt/tests/virtual/sanity/upgrade/upgrade.sh

Lines 18 to 21 in 19ee0b1

	make
	# initialization
	./bin/postgresql-setup --init

We are basically testing a local-only script from the currently prepared build-root (that might be broken), which may easily refer to the installed system-wide scripts (that are not broken). So we might get false positive results.

What we need is to do:

$ sudo make install
$ postgresql-setup

instead of just

./postgresql-setup