Fix $XAPP_DESCRIPTOR_PATH parser bug

While xapp-frame-cpp assumes that $XAPP_DESCRIPTOR_PATH is a filename, the
xapp-onboarder sets it up as a directory. This assumption causes xapps
based on xapp-frame-cpp to crash on startup even using default helm charts.

This change fixes this bug and adds some logic to determine if the
$XAPP_DESCRIPTOR_PATH is a directory or a filename.
This change also adds test cases for $XAPP_DESCRIPTOR_PATH parser.

Issue-ID: RIC-883

Signed-off-by: Alexandre Huff <alexandrehuff@utfpr.edu.br>
Change-Id: I1d29c8c8ae80028accc5d3e29ea571b6365121ac
diff --git a/CMakeLists.txt b/CMakeLists.txt
index a06f3f4..b79eb2e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -30,7 +30,7 @@
 
 set( major_version "2" )		# should be automatically populated from git tag later, but until CI process sets a tag we use this
 set( minor_version "3" )
-set( patch_level "5" )
+set( patch_level "6" )
 
 set( install_root "${CMAKE_INSTALL_PREFIX}" )
 set( install_inc "include/ricxfcpp" )