webos_enhanced_submissions: Enable sanity checks even without tag param

:Release Notes:
In commit 64f0567ada02ef39ac4188813cb422216b902cee I've changed default
WEBOS_GIT_TAG to be empty in order to respect SRCREV variable.
Unfortunately I haven't noticed that sanity checks are applied only when
SRC_URI contains git entry with tag parameter set.

:Detailed Notes:
This fix will enable checking that used SRCREV points to specified
submissions tag and that the SRCREV is included in correct branch.

:Testing Performed:
Only build tested.

:QA Notes:
No change to image.

:Issues Addressed:
[ES-791] Enable webos_enhanced_submissions sanity checks
[BHV-6871] CCC: Enable webos_enhanced_submissions sanity checks

Open-webOS-DCO-1.0-Signed-off-by: Martin Jansa <martin.jansa@lge.com>
Change-Id: I488b14527ff9f124047447878209f8f69eb5babf
Reviewed-on: https://g2g.palm.com/5440
Reviewed-by: DCO Verification
Reviewed-by: Martin Jansa <Martin.Jansa@lge.com>
Tested-by: Martin Jansa <Martin.Jansa@lge.com>
Reviewed-by: Susan Montooth <susan.montooth@lge.com>
Build: Susan Montooth <susan.montooth@lge.com>
Reviewed-by: Build Verification