Fix MySQL lock name length limit

[rob006]

Q	A
Is bugfix?	yes
New feature?	no
Breaks BC?	no
Tests pass?	yes

MySQL 5.7.5 and later enforces a maximum length on lock names of 64 characters. Previously, no limit was enforced.

See symfony/symfony#27250

[samdark]

Merged. Thank you!

[cebe]

Would it be safer to only hash if length is too long? Might break BC with code that syncs lock with other implementation that is not yii

[rob006]

Would it be safer to only hash if length is too long?

That still would be BC break if someone uses MySQL <5.7.5 and has lock name longer than 64 characters - it will be hashed even if there is no need for it.

IMO such condition will add unnecessary complicity and inconsistency. hashLockName() is protected, if someone relies on lock name, he could always override it.