memory leak in Fedora 30

fwupd CI is reporting this issue:

```
14/16 dell-self-test FAIL 0.12 s (exit status 1)
15/16 synapticsmst-self-test OK 0.04 s
16/16 uefi-self-test OK 0.07 s
Ok: 14
Expected Fail: 0
Fail: 1
Unexpected Pass: 0
Skipped: 1
Timeout: 0
The output from the failed tests:
14/16 dell-self-test FAIL 0.12 s (exit status 1)
--- command ---
/build/build/meson-private/dist-build/plugins/dell/dell-self-test
--- stdout ---
/fwupd/plugin{dell:tpm}: OK
/fwupd/plugin{dell:dock}: OK
--- stderr ---
ERROR:esys:src/tss2-esys/esys_tcti_default.c:210:get_tcti_default() No standard TCTI could be loaded
ERROR:esys:src/tss2-esys/esys_context.c:68:Esys_Initialize() Initialize default tcti. ErrorCode (0x00070002)
ERROR:esys:src/tss2-esys/esys_tcti_default.c:210:get_tcti_default() No standard TCTI could be loaded
ERROR:esys:src/tss2-esys/esys_context.c:68:Esys_Initialize() Initialize default tcti. ErrorCode (0x00070002)
ERROR:esys:src/tss2-esys/esys_tcti_default.c:210:get_tcti_default() No standard TCTI could be loaded
ERROR:esys:src/tss2-esys/esys_context.c:68:Esys_Initialize() Initialize default tcti. ErrorCode (0x00070002)
ERROR:esys:src/tss2-esys/esys_tcti_default.c:210:get_tcti_default() No standard TCTI could be loaded
ERROR:esys:src/tss2-esys/esys_context.c:68:Esys_Initialize() Initialize default tcti. ErrorCode (0x00070002)
=================================================================
==3002==ERROR: LeakSanitizer: detected memory leaks
Direct leak of 546 byte(s) in 1 object(s) allocated from:
#0 0x7f04b4a68e56 in __interceptor_calloc (/lib64/libasan.so.5+0x10de56)
#1 0x7f04b4375fd5 (/lib64/libsmbios_c.so.2+0x28fd5)
#2 0x554245445f435f52 ()
Direct leak of 73 byte(s) in 2 object(s) allocated from:
#0 0x7f04b4a68c58 in __interceptor_malloc (/lib64/libasan.so.5+0x10dc58)
#1 0x7f04b4143137 in __vasprintf_internal (/lib64/libc.so.6+0x7a137)
SUMMARY: AddressSanitizer: 619 byte(s) leaked in 3 allocation(s).
-------
```

CI doesn't run on Dell systems, but it seems that there is a memory leak somewhere in a failure path.