Remove mistral from bash-installer

[amanda11]

Removal of postgres and mistral on all platforms from bash one-line installer.

Addresses scripted installer of StackStorm/st2#4762

Covers removal of installation of mistral and postgres by one-line installer. Does not cover changes to Vagrant, docker or packages

Closes #516

[amanda11]

Is it ok to remove mistral completely from installer, or if committed would it affect installs of 3.2.0 - so do we need to check on version of st2 being installed?
e.g. install install mistral if:
a) no version specified (as 3.2.0) still current
b) version specified and < 3.3
The reason I ask is that I see EL6 support had to be re-added to the st2_bootstrap file recently.

[LindsayHill]

@amanda11 when you run curl -sSL https://stackstorm.com/packages/install.sh, that script then pulls the ST2 version branch version of the installer script. It is set to v3.2 right now, and when we release v3.3 it will pull the v3.3 version.

But if you specify an old version, it will pull that old version. So we should be fine with just removing mistral from the master version here, and anyone that deliberately passes an older version flag to the installer should still get an installer script that installs mistral

[blag]

I'd like one more set of eyes on this, but this LGTM.

[arm4b]

👍

[arm4b]

Looks good 👍

Looking closer, we want to merge this PR after removing mistral from the e2e tests, otherwise st2cicd jobs will fail on mistral checks.

It's very helpful to have these PRs organized and prepared around the Mistral removal big task!

[amanda11]

@armab st2tests PR just pushed up (had just finished testing it on the install that had been done using this PR!) - StackStorm/st2tests#190

But I'll also look at the st2ci and st2cd repos...

[blag]

PRs StackStorm/st2ci#189 and StackStorm/st2cd#440 are now merged - it should now be clear to merge this.