microk8s: i/o timeout in coredns pod

Copying from https://github.com/ubuntu/microk8s/issues/958#issuecomment-661986123, as this looks to be the crux of the issue. For some reason, some queries to 8.8.8.8 and 8.8.4.4 for api.jujucharms.com are failing:

[ERROR] plugin/errors: 2 2577415620770853004.8780143945028532492. HINFO: read udp 10.1.21.36:44631->8.8.4.4:53: i/o timeout
[INFO] 10.1.21.38:33385 - 46047 "AAAA IN api.jujucharms.com.localdomain. udp 48 false 512" NOERROR - 0 2.000755655s
[ERROR] plugin/errors: 2 api.jujucharms.com.localdomain. AAAA: read udp 10.1.21.36:57766->8.8.8.8:53: i/o timeout
[INFO] 10.1.21.38:36178 - 22767 "A IN api.jujucharms.com.localdomain. udp 48 false 512" NOERROR - 0 2.000677982s
[ERROR] plugin/errors: 2 api.jujucharms.com.localdomain. A: read udp 10.1.21.36:44211->8.8.8.8:53: i/o timeout
[INFO] 10.1.21.38:60455 - 56232 "AAAA IN api.jujucharms.com.localdomain. udp 48 false 512" NOERROR - 0 2.000352953s
[ERROR] plugin/errors: 2 api.jujucharms.com.localdomain. AAAA: read udp 10.1.21.36:45297->8.8.8.8:53: i/o timeout
[INFO] 10.1.21.38:50299 - 52151 "A IN api.jujucharms.com.localdomain. udp 48 false 512" NOERROR - 0 2.000257257s
[ERROR] plugin/errors: 2 api.jujucharms.com.localdomain. A: read udp 10.1.21.36:40710->8.8.4.4:53: i/o timeout
[INFO] 10.1.21.38:39253 - 3642 "AAAA IN api.jujucharms.com. udp 36 false 512" NOERROR - 0 2.000834815s
[ERROR] plugin/errors: 2 api.jujucharms.com. AAAA: read udp 10.1.21.36:38538->8.8.8.8:53: i/o timeout
[INFO] 10.1.21.38:47372 - 10457 "A IN api.jujucharms.com. udp 36 false 512" NOERROR - 0 2.000768237s
[ERROR] plugin/errors: 2 api.jujucharms.com. A: read udp 10.1.21.36:33745->8.8.4.4:53: i/o timeout
[INFO] 10.1.21.38:47852 - 7227 "AAAA IN api.jujucharms.com. udp 36 false 512" NOERROR - 0 2.000442768s
[ERROR] plugin/errors: 2 api.jujucharms.com. AAAA: read udp 10.1.21.36:42672->8.8.4.4:53: i/o timeout
[INFO] 10.1.21.38:60290 - 23521 "A IN api.jujucharms.com. udp 36 false 512" NOERROR - 0 2.000334072s
[ERROR] plugin/errors: 2 api.jujucharms.com. A: read udp 10.1.21.36:52312->8.8.8.8:53: i/o timeout