Properly default MysqlInnodbBufferPoolSize (overcloud)

In JQ, pipe is for chaining filters. It doesn't mean OR.
So "<anything> | 100" means 100. In the context of the pre-existing
code, this means that 100 will take precedence over a user value. This
patch inverts that precedence.

Fixes Id595113a52f5a1da740bd81a4cf7932c96d57754 .

(Overcloud; undercloud version at
Ic27513170df3ef15ebdf3b3e6f07527a30e656ea)

Change-Id: I5b7c8a27a9348d850d1a6e4ab79304cf13697828
Merge "Properly default MysqlInnodbBufferPoolSize (overcloud)"