Disabled the privilege dropdown for root user

By allowing root user privilege changes to  Operator or Read Only,
after login with root user seeing privilege access issues in some
pages and not possible to change administrator again.

Allowed root user to change password alone and disabled
the privilege changes

Change-Id: I2be93060fb30e1f08dc2ea20a30fb998dc83ee0f
Signed-off-by: aravinths1 <aravinths@ami.com>

src/views/SecurityAndAccess/UserManagement/ModalUser.vue

@@ -109,6 +109,7 @@
                 :options="privilegeTypes"
                 data-test-id="userManagement-select-privilege"
                 :state="getValidationState($v.form.privilege)"
+                :disabled="!newUser && originalUsername === 'root'"
                 @input="$v.form.privilege.$touch()"
               >
                 <template #first>