Limit failures in lsnapshot test_4

The current lsnapshot test bounces the mgs and waits for the initial number of connections to match.

This test fails due to connections not being established or additional connections adding after the mgs is bounced.

The connection count mismatches are not fatal so don't fail when the occur.

In addition an lsnapshot may occur before the lustre file system is fully restored. The snapshot will normally succeed with an additional small delay, so retry the snapshot in such cases.