virt-install: Add support for 'debug' parameter on TPM emulator

E.g.
    virt-install \
    ... \
    --tpm model=tpm-tis,backend.type=emulator,backend.version=2.0,backend.debug=3

  It results in the following domain xml:
  <tpm model="tpm-tis">
    <backend type="emulator" version="2.0" debug="3"/>
  </tpm>

Signed-off-by: Lin Ma <lma@suse.de>

tests/data/cli/compare/virt-install-many-devices.xml

@@ -748,6 +748,9 @@
         <sha512/>
       </active_pcr_banks>
     </tpm>
+    <tpm model="tpm-tis">
+      <backend type="emulator" version="2.0" debug="3"/>
+    </tpm>
     <graphics type="sdl" display=":3.4" xauth="/tmp/.Xauthority">
       <ab>cd</ab>
     </graphics>

tests/test_cli.py

@@ -796,6 +796,8 @@ source.reservations.managed=no,source.reservations.source.type=unix,source.reser
 
 --tpm passthrough,model=tpm-crb,path=/dev/tpm0,backend.encryption.secret=11111111-2222-3333-4444-5555555555,backend.persistent_state=yes,active_pcr_banks.sha1=on,active_pcr_banks.sha256=yes,active_pcr_banks.sha384=yes,active_pcr_banks.sha512=yes,version=2.0
 
+--tpm model=tpm-tis,backend.type=emulator,backend.version=2.0,backend.debug=3
+
 
 --watchdog ib700,action=pause
 

virtinst/cli.py

@@ -4309,6 +4309,7 @@ class ParserTPM(VirtCLIParser):
         cls.add_arg("backend.encryption.secret", "encryption_secret")
         cls.add_arg("backend.persistent_state",
                     "persistent_state", is_onoff=True)
+        cls.add_arg("backend.debug", "debug")
 
         cls.add_arg("active_pcr_banks.sha1",
                     "active_pcr_banks.sha1", is_onoff=True)

virtinst/devices/tpm.py

@@ -41,6 +41,7 @@ class DeviceTpm(Device):
     encryption_secret = XMLProperty("./backend/encryption/@secret")
     persistent_state = XMLProperty(
             "./backend/@persistent_state", is_yesno=True)
+    debug = XMLProperty("./backend/@debug")
 
     active_pcr_banks = XMLChildProperty(_ActivePCRBanks, is_single=True)