Sets method post for playing action

Removes explanation text for non triggered job
Adds tests

app/views/projects/jobs/_empty_state.html.haml

 - illustration = local_assigns.fetch(:illustration)
 - illustration_size = local_assigns.fetch(:illustration_size)
 - title = local_assigns.fetch(:title)
-- content = local_assigns.fetch(:content)
+- content = local_assigns.fetch(:content, nil)
 - action = local_assigns.fetch(:action, nil)
 .row.empty-state
@@ -11,7 +11,8 @@
   .col-xs-12
     .text-content
       %h4.text-center= title
-      %p= content
+      - if content
+        %p= content
       - if action
         .text-center
           = action

app/views/projects/jobs/show.html.haml

@@ -93,14 +93,13 @@
         illustration: 'illustrations/manual_action.svg',
         illustration_size: 'svg-394',
         title: _('This job requires a manual action'),
-        content: _('This job depends on a user to trigger its process. Often they are used to deploy code to production environments.'),
-        action: ( link_to _('Trigger this manual action'), play_project_job_path(@project, @build), class: 'btn btn-primary', title: _('Trigger this manual action') )
+        content: _('This job depends on a user to trigger its process. Often they are used to deploy code to production environments'),
+        action: ( link_to _('Trigger this manual action'), play_project_job_path(@project, @build), method: :post, class: 'btn btn-primary', title: _('Trigger this manual action') )
     - else
       = render 'empty_state',
         illustration: 'illustrations/job_not_triggered.svg',
         illustration_size: 'svg-306',
-        title: _('This job has not been triggered yet'),
-        content: _('This job depends on upstream jobs that need to succeed in order for this job to be triggered.')
+        title: _('This job has not been triggered yet')
   = render "sidebar"

spec/features/projects/jobs_spec.rb

@@ -383,6 +383,11 @@ feature 'Jobs' do
         expect(page).to have_content('This job depends on a user to trigger its process. Often they are used to deploy code to production environments.')
         expect(page).to have_link('Trigger this manual action')
       end
+
+      it 'plays manual action' do
+        click_link 'Trigger this manual action'
+        expect(page).not_to have_link('Trigger this manual action')
+      end
     end
     context 'Non triggered job' do
@@ -392,9 +397,8 @@ feature 'Jobs' do
         visit project_job_path(project, job)
       end
-      it 'shows manual action empty state' do
+      it 'shows empty state' do
         expect(page).to have_content('This job has not been triggered yet')
-        expect(page).to have_content('This job depends on upstream jobs that need to succeed in order for this job to be triggered.')
       end
     end
   end