Power Hypervisor: fix potential segfault

Power Hypervisor: fix potential segfault

I came across this line in the phypOpen function:

char string[strlen(conn->uri->path)];

Here the path part of the given URI is used without checking it for
NULL, this can cause a segfault as strlen expects a string != NULL.
Beside that uuid_db and connection_data leak in case of an error.

In this line

conn->uri->path = string;

the original path of the URI leaks. The patch adds a VIR_FREE call
before setting the new path.

The attached patch is compile-tested but I don't have a Power
Hypervisor installation at hand to test it for real.

Matthias

Signed-off-by: Chris Lalancette <clalance@redhat.com>