Support multiple heatclient versions for SD

The software_deployment resources lazy loads data via the
heatclient _get() function. Not only is this function private
but the oslo-incubator recently reverted things such that
get() should once again be used for lazy loading details.

See oslo-incubator commit 04a1abe59ac39890f57d2eed57d3d1b12bb5d757

This was merged into heatclient master in:

72017c566850da589f7dc7dc275871986aadbd54

This patch makes it so that heat will work with both versions
of heatclient.

Change-Id: I1799636d39cea410b55ffe72eeecba4f4a7a0f80
Closes-bug: #1308770
(cherry picked from commit a7d782395084c6c16304f17d14b824028c5ba450)