bluez-*: add bluetooth activation in pre-conditions steps

This ensures that a tester is not blocked if Bluetooth tests
are not performed in a specific order.

All other bluetooth related test cases already have this
pre-condition.

Signed-off-by: Dylan Aïssi <dylan.aissi@collabora.com>

test-cases/bluez-file-transfer.yaml

@@ -25,6 +25,10 @@ metadata:
 
   pre-conditions:
     - "If running the test on an SDK image, kill the blueman-applet process, as it prevents the test from installing its own pairing agent."
+    - "Please note that connman disables bluetooth by default on a fresh image.
+       If it's already enabled, connmanctl will give an \"In progress\" error that
+       may be ignored. To enable the device:"
+    - $ connmanctl enable bluetooth
 
   expected:
     - "If PASSED is displayed, all of the test have passed. The output should be

test-cases/bluez-phone.yaml

@@ -29,6 +29,10 @@ metadata:
   pre-conditions:
     - "If running the test on an SDK image, kill the blueman-applet process, as
        it prevents the test from installing its own pairing agent."
+    - "Please note that connman disables bluetooth by default on a fresh image.
+       If it's already enabled, connmanctl will give an \"In progress\" error that
+       may be ignored. To enable the device:"
+    - $ connmanctl enable bluetooth
     - "When running the test on SabreLite boards using the headphone jack to
        check the audio output, the audio manager needs to be configured to route it
        accordingly as it defaults to the HDMI output:"