Invalidate stored service password if the endpoint URL is changed

This MR handles bugs (introduced by !1558 (merged)):

• It is not possible to set a new URL and a password at the same time (new password is ignored)
• An error occurs on the Service Templates admin pages (prop_updated? was referencing the service's project, which is not defined for templates)
• Passwords are reset on every save in Service Templates admin pages

Related !1583 (merged)

@rspeicher Please take a look

What do you think about:

value_was = send("#{prop_name}_was")
return false if value_was.nil?

value_was != send(prop_name)

@vsizov One note to address or ignore, your call. Otherwise, LGTM.

Hi,

I believe this would fail the following scenarios:

    it "does not reset password if new url is set together with password, even if it's the same password" do
      @teamcity_service.teamcity_url = 'http://gitlab_edited.com'
      @teamcity_service.password = 'password'
      @teamcity_service.save
      expect(@teamcity_service.password).to eq("password")
      expect(@teamcity_service.teamcity_url).to eq("http://gitlab_edited.com")
    end


    context "when no password was set before" do
      before do
        @teamcity_service = TeamcityService.create(
          project: create(:project),
          properties: {
            teamcity_url: 'http://gitlab.com',
            username: 'mic'
          }
        )
      end

      it "saves password if new url is set together with password" do
        @teamcity_service.teamcity_url = 'http://gitlab_edited.com'
        @teamcity_service.password = 'password'
        @teamcity_service.save
        expect(@teamcity_service.password).to eq("password")
        expect(@teamcity_service.teamcity_url).to eq("http://gitlab_edited.com")
      end
    end

    it "should reset password if url changed, even if setter called multiple times" do
      @teamcity_service.teamcity_url = 'http://gitlab1.com'
      @teamcity_service.teamcity_url = 'http://gitlab1.com'
      @teamcity_service.save
      expect(@teamcity_service.password).to be_nil
    end

@cernvcs You're right, all three of those fail.

@vsizov Please address.

mentioned in merge request !1600 (merged)

Status changed to closed

mentioned in commit 62bf2eb8

mentioned in commit maxraab/gitlab-ce@c0f8b956