ClatdController - add mutex annotations

This effectively makes ClatdController single threaded.
Which makes things nice and simple.

Test: atest libbpf_android_test libnetdbpf_test netd_integration_test netd_unit_test netdutils_test resolv_integration_test resolv_unit_test
Bug: 65674744
Bug: 131268436
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I352761b6c44c17f9ea0897ea821a826f642659d5
Merged-In: I352761b6c44c17f9ea0897ea821a826f642659d5
(cherry picked from commit 56280274)