Having a configuration option 'disable' with default value 'false'
results in a double-negative meaning which can be confusing.
Replace this option with enableReverseDnsLookup, with default 'true',
which effectively results in the same default behavior when no value
is configured.
Rename the DisableReverseDnsLookup and DisableReverseDnsLookupProvider
classes accordingly.
Change-Id: I36a8be9474f58a0d1457850bb5fae2fa7cc08ee8
46a2f6cf4c