Add mysqlctl support for MariaDB 10.4

[morgo]

This adds mysqlctl support for MariaDB 10.4 bootstrapping (technically it tells mariadb 10.4 to bootstrap the old way). MariaDB 10.4 does not work yet, since it fails somewhere around the force master-elect:

+ cd examples/local/
+ ./101_initial_cluster.sh
enter etcd2 env
add /vitess/global
add /vitess/zone1
add zone1 CellInfo
etcd start done...
enter etcd2 env
Starting vtctld...
Access vtctld web UI at http://morgox1:15000
Send commands with: vtctlclient -server morgox1:15999 ...
enter etcd2 env
Starting MySQL for tablet zone1-0000000100...
Starting MySQL for tablet zone1-0000000101...
Starting MySQL for tablet zone1-0000000102...
Starting vttablet for zone1-0000000100...
Access tablet zone1-0000000100 at http://morgox1:15100/debug/status
Starting vttablet for zone1-0000000101...
Access tablet zone1-0000000101 at http://morgox1:15101/debug/status
Starting vttablet for zone1-0000000102...
Access tablet zone1-0000000102 at http://morgox1:15102/debug/status
Waiting for tablets to be listening...
Tablets up!
W1029 13:40:15.140647   10388 main.go:64] W1029 19:40:15.138686 reparent.go:182] master-elect tablet zone1-0000000100 is not the shard master, proceeding anyway as -force was used
W1029 13:40:15.141158   10388 main.go:64] W1029 19:40:15.139772 reparent.go:188] master-elect tablet zone1-0000000100 is not a master in the shard, proceeding anyway as -force was used
E1029 13:40:45.661848   10388 main.go:67] remote error: rpc error: code = Unknown desc = tablet zone1-0000000101 InitSlave failed: rpc error: code = DeadlineExceeded desc = context deadline exceeded;tablet zone1-0000000102 InitSlave failed: rpc error: code = DeadlineExceeded desc = context deadline exceeded

After this merges, I will update #5362 to say this is no longer a mysqlctl issue, but a reparenting issue that needs further investigation.

Signed-off-by: Morgan Tocker tocker@gmail.com