BigSwitch: Stop using external locks
BigSwitch: Stop using external locks

Changes BigSwitch server manager REST lock
to an in-memory lock since the plugin isn't
expected to run in independent processes.

Closes-Bug: #1284881
Change-Id: I2fdd5ba79a0c4b94b2b410db54a63f7c0ca47525

stackforge/networking-bigswitch,wolverineav/networking-bigswitch,wolverineav/networking-bigswitch,openstack/networking-bigswitch,stackforge/networking-bigswitch,openstack/networking-bigswitch