[Test] Fix MTS failure on GetAddrinfo_BlockDnsQueryWithUidRule

The test has different expected behavior when the device under test has
the libcom.android.tethering.dns_helper and does not have the library.
The test needs to check whether the libcom.android.tethering.dns_helper
is installed or not.

Bug: 309164580
Test: atest resolv_integration_test:ResolverTest#GetAddrinfo_BlockDnsQue
ryWithUidRule

Change-Id: I0b54224634e873374566fa5bf83c9d0af352e84d