Fix Sensors HAL 1.0 VTS tests

HAL 1.0 VTS tests need to detach the polling thread or it will never
exit on its own. Additionally, the poll() methods return status needs to
be checked or HIDL will assert and cause the program to crash.

Bug: 150475314
Test: atest VtsHalSensorsV1_0TargetTest VtsHalSensorsV2_0TargetTest
Change-Id: I626b7aa064a1f258c968d1787872b9c67786dede