Including the ldms_xprt.h library

[Snell1224]

The ldms_xprt.h library was removed in ldms_stream.h in a previous commit and caused compile failures with the darshanConnector code.

I would prefer to add this back in but if there are issues with this, I can always explicitly include it in the darshanConnector code.

[tom95858]

@narategithub can you please take a look at this?

[narategithub]

@tom95858 I think this is not required. The application only include "ldms.h" and got everything needed to use LDMS Rail + Stream. 'ldms_stream.h' is private to LDMS internal.

[Snell1224]

@narategithub @tom95858 I am checking if the ldms_t struct is connected to the daemon with:
if (<struct_name>->disconnected)

However, I receive the error:

invalid use of undefined type ‘struct ldms_xprt’

if ldms_xprt.h is not included.

I'm sure most developers won't be trying to use the variables in the ldms_t struct and that this is just an unusual case so I'll go ahead and include ldms_xprt.h in the darshanConnector code and close this PR.

I figured I'd bring it up in case someone else has the same/similar issue later on when implementing an LDMS streams connector and are wanting to use the ldms_t variables.