utils.FileLock: handle init errors properly
utils.FileLock: handle init errors properly

If the open of the lock file fails (due to whatever reason), 'self'
won't have the 'fd' attribute, and thus we fail in Close/__del__, which
will ruin proper error reporting:

IOError: [Errno 30] Read-only file system: '/var/lib/ganeti/queue/lock'
Exception exceptions.AttributeError: "'FileLock' object has no attribute
'fd'" in <bound method FileLock.__del__ of <ganeti.utils.FileLock object
at 0x2aaaad0bebd0>> ignored

Signed-off-by: Iustin Pop <acf83a5274f31a43af6b914614365999469c1a31@google.com>
Reviewed-by: Michael Hanselmann <68b67885ff74281219b4a4be33cc20fd45078d7c@google.com>

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