Switch to using BASH_VERSINFO rather than BASH_VERSION, since it
provides structured data.
BASH_VERSINFO
A readonly array variable whose members hold version information for this instance of bash. The values assigned to the array members are as follows:
BASH_VERSINFO[0] The major version number (the release).
BASH_VERSINFO[1] The minor version number (the version).
BASH_VERSINFO[2] The patch level.
BASH_VERSINFO[3] The build version.
BASH_VERSINFO[4] The release status (e.g., beta1).
BASH_VERSINFO[5] The value of MACHTYPE.
When release status is not "release", bash builds are in debug mode and
output extra information which disturbs the integration.
Closes#5473
f0d497dfe0