Use parted ansible module for partition removal

Tasks using this module should be more immutable rather than failing
when these partitions have already been removed.

Also remove parted from dependencies in gitian section

since it is required earlier in the 'common' section

roles/common/tasks/repartition.yml

@@ -17,12 +17,16 @@
     state: absent
 
 - name: Remove partition number 5
-  command: parted --script /dev/sda rm 5
-  become: yes
+  parted:
+    device: /dev/sda
+    number: 5
+    state: absent
 
 - name: Remove partition number 2
-  command: parted --script /dev/sda rm 2
-  become: yes
+  parted:
+    device: /dev/sda
+    number: 2
+    state: absent
 
 - name: Resize partition number 1 to fill the available space on the disk
   command: parted ---pretend-input-tty /dev/sda unit % resizepart 1 yes 100

roles/gitian/tasks/main.yml

@@ -25,7 +25,6 @@
     - kpartx
     - lintian
     - make
-    - parted
     - python-cheetah
     - qemu-utils
     - ruby