hyperv: Avoid memleak in hypervDomainDefParsePhysicalDisk

hyperv: Avoid memleak in hypervDomainDefParsePhysicalDisk

When parsing a physical disk, the @hostResouce is escaped once
with the retval being stored into @hostEscaped. Then, it's
escaped again, but the retval is stored into the very same
variable, leading to a leak where intermediate value is lost.

256 bytes in 1 blocks are definitely lost in loss record 469 of 483
   at 0x49543A0: realloc (vg_replace_malloc.c:1804)
   by 0x516C251: g_realloc (in /usr/lib64/libglib-2.0.so.0.8400.4)
   by 0x518BB7E: g_string_expand (in /usr/lib64/libglib-2.0.so.0.8400.4)
   by 0x518BFF9: g_string_insert_len (in /usr/lib64/libglib-2.0.so.0.8400.4)
   by 0x4A58B5F: g_string_append_len_inline (gstring.h:247)
   by 0x4A58B5F: virBufferAdd (virbuffer.c:164)
   by 0x4AFDA71: virStringReplace (virstring.c:708)
   by 0x4DA4381: hypervDomainDefParsePhysicalDisk (hyperv_driver.c:1375)
   by 0x4DA4A18: hypervDomainDefParseStorage (hyperv_driver.c:1487)
   by 0x4DA9E31: hypervDomainGetXMLDesc (hyperv_driver.c:2761)
   by 0x4DFB3E5: virDomainGetXMLDesc (libvirt-domain.c:2898)
   by 0x406D39B: cmdDumpXML (virsh-domain.c:10787)
   by 0x40B13B1: vshCommandRun (vsh.c:1383)

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>