Add a missing case for BTA_DM_SEARCH_CANCEL_CMPL_EVT

Cancelling discovery was not handled properly in
btif_dm_search_services_evt and was causing crashes due to assert in
default case.

Bug: 31442085
Change-Id: If9a2c203730c9b06df5ff8d8e251f0c35addcb82
(cherry picked from commit 7df43240c4a7cf5ecd58a39f03d235bf52929d79)