reduce log output for DHCP services

[bcressey]

Issue number:
Fixes #2254

Description of changes:
Changing the log level to "notice" makes it so only new and renewed leases are logged, rather than every step of the lease negotiation process.

Testing done:
Verified that the remaining output consists of messages like these:

Jul 04 16:22:04.002962 localhost wickedd-dhcp4[1521]: eth0: Request to acquire DHCPv4 lease with UUID ab13c362-fe3f-0f00-0306-000002000000
Jul 04 16:22:04.004096 localhost wickedd-dhcp6[1522]: eth0: Request to acquire DHCPv6 lease with UUID ab13c362-fe3f-0f00-0306-000003000000 in mode auto
Jul 04 16:22:04.644916 localhost wickedd-dhcp4[1521]: eth0: Committed DHCPv4 lease with address 10.0.85.39 (lease time 3600 sec, renew in 1800 sec, rebind in 3150 sec)
Jul 04 16:22:05.967654 localhost wickedd-dhcp6[1522]: eth0: Committing DHCPv6 lease with:
Jul 04 16:22:05.967681 localhost wickedd-dhcp6[1522]: eth0    +ia-na.address 2600:1f14:ae2:f103:baa1:f578:6e8a:6b0e/0, pref-lft 140, valid-lft 450
Jul 04 16:23:16.657088 localhost wickedd-dhcp6[1522]: eth0: Committing DHCPv6 lease with:
Jul 04 16:23:16.657114 localhost wickedd-dhcp6[1522]: eth0    +ia-na.address 2600:1f14:ae2:f103:baa1:f578:6e8a:6b0e/0, pref-lft 140, valid-lft 450
Jul 04 16:24:26.668959 localhost wickedd-dhcp6[1522]: eth0: Committing DHCPv6 lease with:
Jul 04 16:24:26.668975 localhost wickedd-dhcp6[1522]: eth0    +ia-na.address 2600:1f14:ae2:f103:baa1:f578:6e8a:6b0e/0, pref-lft 140, valid-lft 450

In steady state in EC2, this results in two log entries every 70 seconds for DHCPv6 leases, and one log entry every 30 minutes for DHCPv4 leases.

Terms of contribution:

By submitting this pull request, I agree that this contribution is dual-licensed under the terms of both the Apache License, version 2.0, and the MIT license.