Multiple DHCP ranges for Ironic Inspector

Add a new parameter 'ironic_dnsmasq_dhcp_ranges' and enable the
configuration of the corresponding 'dhcp-range' and 'dhcp-option'
blocks in Ironic Inspector dnsmasq for multiple ranges.

The old parameters 'ironic_dnsmasq_dhcp_range' and
'ironic_dnsmasq_default_gateway' used for the only range are now
removed.

This change implements the same solution used in the TripleO several
years ago in the: Ie49b07ffe948576f5d9330cf11ee014aef4b282d

Also, this change contains: Iae15e9db0acc2ecd5b087a9ca430be948bc3e649
fix for lease time.
The value can be changed globally or per range.

Change-Id: Ib69fc0017b3bfbc8da4dfd4301710fbf88be661a
Signed-off-by: Maksim Malchuk <maksim.malchuk@gmail.com>
Co-Authored-By: Radosław Piliszek <radoslaw.piliszek@gmail.com>