rx: Lock call for KeepAliveOn/KeepAliveOff

rx: Lock call for KeepAliveOn/KeepAliveOff

rxi_KeepAliveOn/Off expect the call lock to be held after the call has
been initialized. So, hold it in the rx_KeepAliveOn/Off callers.

Reviewed-on: http://gerrit.openafs.org/8463
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Simon Wilkinson <simonxwilkinson@gmail.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
(cherry picked from commit 866c05825c9964aa92740bcb0f20f26b451e65ea)

Change-Id: I2df1937f4098dde59a7fed344e1c975fdf0cdf1b
Reviewed-on: http://gerrit.openafs.org/8551
Reviewed-by: Ken Dreyer <ktdreyer@ktdreyer.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Paul Smeddle <paul.smeddle@gmail.com>