Support DRBD 8.4.3 command syntax
Support DRBD 8.4.3 command syntax

DRBD 8.4.3 does not support specifying volume ids directly while
creating the meta device. It requires a slightly different syntax (using
flex-external as volume id) which is fortunately also supported by (at
least) DRBD 8.4.2.

Signed-off-by: Thomas Thrainer <98bdeac947eb8ca18146e9ce7f092788ec242cd1@google.com>
Reviewed-by: Guido Trotter <f62ca4d5358bdaeef0e50e57f9f7e231de63727e@google.com>

yiannist/ganeti,mbakke/ganeti,grnet/snf-ganeti,leshchevds/ganeti,bitemyapp/ganeti,yiannist/ganeti,ganeti-github-testing/ganeti-test-1,apyrgio/ganeti,leshchevds/ganeti,yiannist/ganeti,ganeti/ganeti,mbakke/ganeti,dimara/ganeti,ganeti-github-testing/ganeti-test-1,ganeti/ganeti,leshchevds/ganeti,mbakke/ganeti,dimara/ganeti,onponomarev/ganeti,andir/ganeti,andir/ganeti,onponomarev/ganeti,apyrgio/ganeti,grnet/snf-ganeti,apyrgio/snf-ganeti,apyrgio/snf-ganeti,bitemyapp/ganeti,ganeti/ganeti,andir/ganeti