volla-mimameid: fix coming (back) from Android

- If the current slot is 'b' (as it can be if Android has been updated),
  even if we set the (new) active slot to 'a', we still have to
  explicitly spell out the slot, otherwise bootloader will still
  flash to slot b.
- vbmeta has to be flashed, replacing the one from Android. The new
  bootstrap tarball is provided by Volla to include vbmeta.

v2/devices/mimameid.yml

@@ -53,9 +53,9 @@ operating_systems:
           - core:download:
               group: "firmware"
               files:
-                - url: "https://volla.tech/filedump/volla-mimameid-11.0-ubports-installer-bootstrap.zip"
+                - url: "https://volla.tech/filedump/volla-mimameid-11.0-ubports-installer-bootstrap-v2.zip"
                   checksum:
-                    sum: "c0216239cc6dc11e23940884d0f6d1183b29898e63b561da8122bf69636f6c7c"
+                    sum: "82ec6dd3d5602ecdd5cd445e09440c6c764b841648c22317a59ca536c502323b"
                     algorithm: "sha256"
         condition:
           var: "bootstrap"
@@ -64,7 +64,7 @@ operating_systems:
           - core:unpack:
               group: "firmware"
               files:
-                - archive: "volla-mimameid-11.0-ubports-installer-bootstrap.zip"
+                - archive: "volla-mimameid-11.0-ubports-installer-bootstrap-v2.zip"
                   dir: "unpacked"
         condition:
           var: "bootstrap"
@@ -87,12 +87,16 @@ operating_systems:
       - actions:
           - fastboot:flash:
               partitions:
-                - partition: "lk"
+                - partition: "lk_a"
                   file: "unpacked/lk.img"
                   group: "firmware"
-                - partition: "boot"
+                - partition: "boot_a"
                   file: "unpacked/boot.img"
                   group: "firmware"
+                - partition: "vbmeta_a"
+                  file: "unpacked/vbmeta.img"
+                  group: "firmware"
+                  flags: [ "--disable-verity" ]
                 - partition: "super"
                   file: "unpacked/super.img"
                   group: "firmware"
@@ -333,13 +337,13 @@ operating_systems:
       - actions:
           - fastboot:flash:
               partitions:
-                - partition: "dtbo"
+                - partition: "dtbo_a"
                   file: "unpacked_droidian/data/dtbo.img"
                   group: "firmware"
-                - partition: "boot"
+                - partition: "boot_a"
                   file: "unpacked_droidian/data/boot.img"
                   group: "firmware"
-                - partition: "vbmeta"
+                - partition: "vbmeta_a"
                   file: "unpacked_droidian/data/vbmeta.img"
                   group: "firmware"
                 - partition: "userdata"