postgresql: Update setup-disks to use `service postgresql`.
postgresql: Update setup-disks to use `service postgresql`.

Using `service postgresql` makes it no longer linked to the specific
version/cluster that is on the host.

shubhamdhama/zulip,synicalsyntax/zulip,eeshangarg/zulip,timabbott/zulip,brainwane/zulip,brainwane/zulip,zulip/zulip,showell/zulip,rht/zulip,showell/zulip,zulip/zulip,eeshangarg/zulip,zulip/zulip,andersk/zulip,hackerkid/zulip,andersk/zulip,zulip/zulip,brainwane/zulip,kou/zulip,punchagan/zulip,eeshangarg/zulip,kou/zulip,andersk/zulip,timabbott/zulip,rht/zulip,rht/zulip,shubhamdhama/zulip,kou/zulip,rht/zulip,kou/zulip,punchagan/zulip,kou/zulip,kou/zulip,punchagan/zulip,showell/zulip,timabbott/zulip,brainwane/zulip,andersk/zulip,showell/zulip,timabbott/zulip,brainwane/zulip,zulip/zulip,kou/zulip,andersk/zulip,shubhamdhama/zulip,brainwane/zulip,eeshangarg/zulip,hackerkid/zulip,synicalsyntax/zulip,punchagan/zulip,timabbott/zulip,rht/zulip,eeshangarg/zulip,zulip/zulip,synicalsyntax/zulip,zulip/zulip,synicalsyntax/zulip,shubhamdhama/zulip,eeshangarg/zulip,hackerkid/zulip,synicalsyntax/zulip,andersk/zulip,hackerkid/zulip,timabbott/zulip,shubhamdhama/zulip,hackerkid/zulip,timabbott/zulip,punchagan/zulip,punchagan/zulip,showell/zulip,punchagan/zulip,andersk/zulip,rht/zulip,shubhamdhama/zulip,eeshangarg/zulip,hackerkid/zulip,synicalsyntax/zulip,brainwane/zulip,showell/zulip,shubhamdhama/zulip,showell/zulip,rht/zulip,hackerkid/zulip,synicalsyntax/zulip