bionic: Support case-insensitive domain name hash

- Correct bytes hashing in DNS packet i.e., decrease number
  of bytes, otherwise whole of DNS packet is getting parsed
  and hashed resulting in not taking "Query Records" in DNS
  packet into account as intended.

- Support case-insensitive hashing i.e., convert domain names
  into lowercase before hashing/comparison so that there is
  no additional query when domain names are same.

Test: as follows
      - build, and boot walleye
      - netd_test passes
      - Perform DNS queries, and ensure they are not case sensitive and
        verify that there is no additional DNS query

CRs-Fixed: 2268427
Change-Id: Idb517b8eca8c8a6ac9d2d9a2fbb08bda68958fcb