CA-161590: purge cached stunnel connections (to master) along force_connection_reset
CA-161590: purge cached stunnel connections (to master) along force_connection_reset

When force_connection_reset is called usually when the connection to master has
been cut off abruptly. It's very likely the same problem is happening on all
other connections to the  master. It's wise to just purge them, otherwise some
process might be blocked by using these outdated connections. Though this won't
help those connections which have been pop out and are in use.

Signed-off-by: Zheng Li <34c6fceca75e456f25e7e99531e2425c6c1de443@zheng.li>
(cherry picked from commit 0239744085d7657c579bd8765c17e3b6ddcc0ee5)

robertbreker/xen-api,robertbreker/xen-api,agimofcarmen/xen-api,vasilenkomike/xen-api,robertbreker/xen-api,guard163/xen-api,rafalmiel/xen-api,vasilenkomike/xen-api,djs55/xen-api,srowe/xen-api,guard163/xen-api,rafalmiel/xen-api,simonjbeaumont/xen-api,simonjbeaumont/xen-api,jjd27/xen-api,agimofcarmen/xen-api,salvocambria/xen-api,salvocambria/xen-api,djs55/xen-api,srowe/xen-api,robertbreker/xen-api,salvocambria/xen-api,jjd27/xen-api,anoobs/xen-api,jjd27/xen-api,simonjbeaumont/xen-api,thomassa/xen-api,agimofcarmen/xen-api,srowe/xen-api,djs55/xen-api,Frezzle/xen-api,rafalmiel/xen-api,koushikcgit/xen-api,jjd27/xen-api,simonjbeaumont/xen-api,agimofcarmen/xen-api,anoobs/xen-api,srowe/xen-api,agimofcarmen/xen-api,thomassa/xen-api,euanh/xen-api,Frezzle/xen-api,anoobs/xen-api,agimofcarmen/xen-api,simonjbeaumont/xen-api,anoobs/xen-api,koushikcgit/xen-api,Frezzle/xen-api,koushikcgit/xen-api,guard163/xen-api,euanh/xen-api,koushikcgit/xen-api,thomassa/xen-api,thomassa/xen-api,djs55/xen-api,vasilenkomike/xen-api,salvocambria/xen-api,srowe/xen-api,vasilenkomike/xen-api,djs55/xen-api,Frezzle/xen-api,euanh/xen-api,Frezzle/xen-api,anoobs/xen-api,koushikcgit/xen-api,robertbreker/xen-api,robertbreker/xen-api,euanh/xen-api,salvocambria/xen-api,vasilenkomike/xen-api,jjd27/xen-api,anoobs/xen-api,vasilenkomike/xen-api,simonjbeaumont/xen-api,guard163/xen-api,guard163/xen-api,rafalmiel/xen-api,jjd27/xen-api,thomassa/xen-api,euanh/xen-api,thomassa/xen-api,salvocambria/xen-api,djs55/xen-api,rafalmiel/xen-api,guard163/xen-api,koushikcgit/xen-api,rafalmiel/xen-api,euanh/xen-api