Use ant isset task instead of hoaky workaround

• Type: Bug
• Status: Closed
• Resolution: Fixed
• Affects Version/s: 5.1.2, 5.2.3, 6.0.0 Preview
• Fix Version/s: None
• Component/s: Legacy
• Labels: None
• Branch Version/s:
  5.2.x, 5.1.x
• Backported to Branch:
  Committed

1.)

This:

<equals arg1="${theme.type}" arg2="$${theme.type}" />

Becomes:

<not>
<isset property="theme.type" />
</not>

2.)

This:

<not>
<equals arg1="${sql.version}" arg2="$${sql.version}" />
</not>

Becomes:

<isset property="sql.version" />